• Prepare a tray by lining it with parchment paper (if rigid), or simply oiling it (if flexible).

  (If you are making a half can of condensed milk batch of fudge, a regular takeaway tray is the ideal size! If making a larger batch, either use two trays, or a 7–8" (18–20 cm) square pan.) 
• Pour the condensed milk into a microwave-proof jug or bowl. Add the Nutella, and break the chocolate into pieces before adding this too.
• Put the jug in the microwave on half power and heat in 30 second bursts, stirring well each time. Stop before the last pieces of chocolate are fully dissolved.
• Give the mixture a good continuous stir until the last of the chocolate has melted and the mixture is smooth.
• Pour the Nutella fudge into the prepared tray, and smooth the top. Allow to cool and then place in the fridge to set for about 4 hours.
• Cut into squares, ready to serve. Store the fudge in a covered container in the fridge.

To make on the stove

• Prepare the tray.
• Break up the chocolate and put it on top of the milk. Put all the ingredients in a saucepan.
• Set the pan on the lowest heat and once the chocolate starts to melt, keep stirring it. Do not leave the pan, as it can rapidly overheat. If this happens, the mixture will split, spoiling your fudge.
• When you have a smooth mixture, pour the fudge into the tray. Smooth out the top and once cool. put in the fridge to set for 4 hours or overnight. 

To make in the slow cooker

• Prepare the tray or tin. Break up the chocolate and put all the ingredients in a bowl or jug.
• Stand the jug in the slow cooker. Add a few inches of boiling water to the slow cooker pot so that it surrounds the bowl.
• Set the cooker to low. It is essential that you leave the lid off, because you do not want the water to condense drip into your fudge.
• Stir the fudge occasionally, taking care not to get any water into the mixture. The chocolate will melt and combine with the other ingredients. When you have a smooth mixture, carefully remove the bowl or jug.
• Pour the fudge into the tray and when cooled, allow to set in the fridge for about 4 hours.