Onion sauce is a British classic that is so easy to make. Packed with flavour from the sweet braised onions, served in a creamy white sauce it is a delicious traditional accompaniment to a roast, and easy way to make it go further. Try my recipe that is just like the one my Grandmother made!
Onion sauce
Onion sauce is a traditional accompaniment to a roast dinner, which in recent years has become less popular than it once was.
This really is rather a shame as onion sauce is so delicious and simple to make, and also an easy and affordable way to make the expensive part of the meal (the meat) go further.
See Also
- Diane sauce is a retro classic easy recipe,
- Quick and easy Stilton sauce – Intense and delicious
- Parsley sauce – A British classic, usually served with fish
- More sauces, dips and dressings
When I was a child onion sauce would be a regular with our Sunday roast, with leftovers reheated and served with the leftovers from the joint on a Monday.
I now often whizz leftovers into a batch of soup – where it adds flavour and a layer of creaminess.
Onion sauce tastes sweet and creamy, with all the sharpness of the onion cooked away to a sweetness, so it enhances the flavour of the meat, rather than taking over. I like to add a little cream for an extra creamy onion sauce, but it is still delicious without the cream.
I know that making a full roast can be a bit of a juggling act, there are so many parts to the meal, none of them are that difficult, but everything seems to need doing at the same time and timing can be tricky to get everything to come together at the end.
To make things easier you can make your onion sauce in advance.
I like to make it as soon as the meat goes into the oven, and then reheat just before serving, but you can also make the day before. I often make a double batch and freezer half for the next roast dinner – cook once and eat twice.
Why make onion sauce
- It’s delicious! The combination of the umami from the onion and the richness of the cream makes a winning sauce
- Not just for roasts – onion sauce lifts the simplest dishes. Simply fry off or grill a chop or chicken breast, add onion sauce and voila – an instant bistro-worthy dish
- It’s so easy to make, and uses everyday ingredients
- Easy sides like this make the expensive part of the meal – the meat – go much further.
Onion sauce ingredients
- Onions – Regular medium sized brown onions. Not red onions.
- Butter – Salted or unsalted – it does not matter – if using salted add a little less salt when seasoning.
- Flour – Regular plain white / all purpose flour.
- Milk – I used semi skimmed, but it really does not matter, especially as I’m adding cream.
- Cream – UK double cream / US heavy cream. The cream is optional but the final onion sauce is richer and creamier if you use it.
If you only have a thinner pouring / whipping cream use twice the amount and reduce the milk accordingly.
- Seasoning – I use white pepper for appearance’s sake, so the sauce does not have flecks of black in it.
Both white and black pepper come from the same plant but the pepper berries are processed differently: there is no appreciable difference in flavour. If you only have black pepper, then use that, and grind as finely as you can. There is no need to buy white pepper especially for this recipe.
How to make onion sauce – step by step
Before you start, read my step-by-step instructions, with photos, hints and tips so you can make this perfectly every time.
Scroll down for the recipe card with quantities and more tips at the bottom of the page.
Step One – Peel and dice the onions – about 1cm / 1/3″pieces.
Step Two – Melt the butter in a medium saucepan. Add the onions and stir.
Put the lid on, turn the heat right down and let the onions slowly cook for about 15 minutes, checking and stirring from time to time.
You want the onions to cook, soften and sweeten, but not have too much colour on them. If they start to darken beyond a pale gold the heat is too high.
Helen’s Fuss Free Tip
I use a heat diffuser on my gas cooker to further reduce the heat and get rid of any hot spots. Using a heavy saucepan will also help the onions to cook without browning.
Step Three – Once the onions are cooked make the roux by adding the flour, stir it in, and cook for a few minutes.
The flour needs to be properly cooked, or the final sauce will taste floury.
Slowly stir in the milk, a little at a time, mixing to a smooth paste each time before adding more. Going slowly at this stage will stop your sauce forming lumps, which will be impossible to get out.
Step Four – stir in the rest of the milk, and the cream. Add more liquid if needed for a runnier sauce.
Season to taste.
Serving suggestions
This sauce is goes well with simply cooked meat – chops, chicken breast and so on. It also lifts mashed potato or roasted vegetables.
If making in advance, reheat the sauce slowly and add more milk, if needed, to thin.
Whizz leftovers into soup – it adds a depth of flavour and creaminess. I have done this a few times and have been astonished at how well this works.
Variations
- Smooth onion sauce – blitz with a stick blender
- Mild onion sauce – put the chopped onion in a sieve and pour over a kettle of boiling water before sautéing.
- Infuse with a few cloves or a bay leaf – remove before serving.
Storage & Leftovers
Fridge – Keep your onion sauce in a airtight container or jar for up to 3 days.
Reheating – Bring to a simmer in a small pan over a gentle heat. If needed add some more milk to thin.
Freezer – Freeze in air tight pots, defrost in the fridge before reheating.
Hints and tips
- Cook the onions slowly – you want them soft and sweet. not browned.
- When making the roux – flour and butter mixture – cook the flour properly for at least a couple of minutes to avoid the final sauce tasing of flour.
- Add the milk to the roux slowly, making sure you have a smooth paste before adding more to avoid lumps. After the first few additions you can add a bit faster.
FAQS
Absolutely, yes. Freeze in air tight container, and allow to defrost completely before reheating.
More classic sauces
Mint sauce – the classic pairing with roast lamb
BBQ sauce – far better when homemade
Burger sauce – quick and easy at home, delicious for dipping chips
Peri Peri sauce – homemade Nandos sauce!
Easy Onion Sauce
Ingredients
- 200 g onions (2 medium) (1)
- 30 g (2 tbsp) butter (2)
- 1 tbsp plain flour (all purpose flour)
- 200 ml (5/6 cup) milk (3)
- 60 ml (1/4 cup) double cream / heavy cream (4)
- white pepper and salt (5)
Instructions
- Prepare the onions Peel and dice the onions into about 1cm / 1/3?pieces.200 g onions (2 medium)
- Sauté the onions Melt the butter in a medium saucepan. Add the onions and stir. Put the lid on, turn the heat right down and let the onions slowly cook for about 15 minutes, checking and stirring from time to time.You want the onions to cook, soften and sweeten, but not have too much colour on them. If they start to darken beyond a pale gold the heat is too high. I use a heat diffuser on my gas cooker to further reduce the heat and get rid of any hot spots. Using a heavy saucepan will also help the onions to cook without browning.30 g butter
- Make the roux Once the onions are cooked add the flour, stir it in, and cook for a few minutes.The flour needs to be properly cooked, or the final sauce will taste floury.1 tbsp plain flour (all purpose flour), 200 ml milk
- Make the sauce Slowly stir in the milk, a little at a time, mixing to a smooth paste each time, before adding more. Going slowly at this stage will stop your sauce forming lumps. which are impossible to get out.Stir in the rest of the milk, and the cream. Add more liquid if needed for a runnier sauce.60 ml double cream / heavy cream
- Season to tastewhite pepper and salt
Notes
- Onions – Regular medium sized brown onions.
- Butter – Salted / unsalted it does not matter – if using salted add a little less salt when seasoning.
- Milk – I used semi skimmed, but it really does not matter that much.
- Cream – UK double cream / US heavy cream. The cream is optional but the final onion sauce is richer and creamier if you use it. If you only have a thinner pouring / whipping cream use twice the amount and reduce the milk accordingly.
- Seasoning – White pepper is for appearance only, so the sauce does not have flecks of black in it. Both white and black pepper come from the same plant but the pepper berries are processed differently. There is no appreciable difference in flavour in this recipe. If you only have black pepper use it, and grind as finely as you can. There is no need to buy white pepper especially.
- Smooth onion sauce – blitz the finish sauce with a stick blender
- Mild onion sauce – put the chopped onion in a sieve and pour over a kettle of boiling water before sautéing them.
- Infuse with a few cloves or bay leaf – remove before serving.
- Fridge – Keep your onion sauce in a airtight container or jar for up to 3 days.
- Reheating – Bring to a simmer in a small pan over a gentle heat. If needed add some more milk to thin.
- Freezer – Freeze in air tight pots, defrost in the fridge before reheating.
- Cook the onions slowly – you want them soft and sweet rather than browned.
- When making the roux – flour and butter mixture – cook the flour properly for at least a couple of minutes.
- Add the milk to the roux slowly, making sure you have a smooth paste before adding more. After the first few additions you can add a bit faster.
John Marshall
Never heard of onion sauce…….sounds brill. Will use as is with your suggestions but will also blitz it with garlic, onion and chilli powder
for my ribeye steak.