Don’t skip the cold plate test. It’s the best way to know if your caramel is ready.
The caramel needs to be warm when poured and the base needs to be completely cool.
Once topped, chill the millionaire for 30 minutes to set. However, you don’t want it to get too cold or it’s difficult to cut (with the exception of the vegan version, which is softer).
To cut, use a large deep-bladed knife. Heat the knife in a jug of hot water and then dry it off. The hot blade will melt through the chocolate, making it much easier to cut.
All the millionaires will keep for up to three days if you keep them cool and covered. The vegan millionaire is best kept in the fridge.