1 Heat a double boiler to a nice simmer. 2 Mix all the ingredients (except the nuts) together in a bowl. Mix up the sugar as best you can. 3 Pour mixture in the double boiler and cook stirring fairly constantly until mixture is nice and thick but especially as it gets thicker. 4 Cover with Saran Wrap and cool in the fridge until well chilled. Add nuts if you want them. 5 I usually split my cake layer, either round, square or 9 X 13, and put filling in between the layers and then frost the cake. Makes almost 3 cups of filling. I love fluffy white frosting on any cake with this filling.