For 3-4p melt 50 grams of butter. Add 75 grams of caster sugar (okay, this is not for every day;-)). Mix thoroughly. Add zeste of 1 lemon and 2 egg yolks. Mix again. Add ½ teaspoon of baking powder and 1 table spoon of corn starch. Mix again (with a whisk) and add 40 ml of lemon juice and 125 ml of semi skimmed milk. Beat the 2 egg whites up to snow. Mix gently with the lemon mixture. Put the mixture in greased recipients (1 larger of 4 smaller ones). Put the ovendishes in a larger oven dish filled with 2 cm of warm water. Bake in the oven at 160° for approx 30-40 mins. Serve immediately. Whipped cream, fresh fruit or some powder sugar are optional.