In a jug mix the yeast, warm milk and tablespoon of sugar.
Leave to froth for 10 minutes if you have time then add the melted butter and egg yolks.
Mix this into the flours, with the salt.
Knead for 5-10 minutes on a floured surface or in your food mixer with a dough hook for 5 minutes.
Put in a large bowl with a plate on top and leave in a warm place until doubled in size (1-2 hours)
Knock down and flatten out until it's about the size of a large baking tray.
Slather with the very soft 100g ofbutter.
Sprinkle with the mix of brown sugar and cinnamon, and the sultanas.
Roll up so you have a long swiss roll type thing.
Slice into 2" slices and place in a deep cake tin
I used a 26cm Kaiser tin, with a bit of butter rubbed into it.
Allow to rise for another 1/2 hour. Tuck in any sultanas so they don't burn.
Bake at 200c for 10 minutes
Cover loosely with foil and bake for another 15 minutes or so.
At this point I brush it with a little melted butter and put it back in if not quite cooked through but it's probably not necessary. I am a born fiddler.
Tip out straight away - using a plate to tip it onto then back onto a 2nd plate.
Top with the warm buttery icing and leave to cool....as long as you can bear it.
They are still good on day two (and even better when warmed for 20 seconds in the microwave)