1.Preheat the oven to 175C (350F) and line 12 muffin tins with paper cupcakes liners.
2.Beat eggs, caster sugar and vanilla sugar until light and fluffy.
3.Melt the butter, add the milk and mix with the batter. (Chocolate cupcakes: also add the coffee)
4.Mix flour, baking powder and salt and add to the batter. (Chocolate cupcakes: also add cacao)
5.Add zest and juice from the lemon. (Not for chocolate cupcakes, instead melt the chocolate and stir into the batter)
6.Bake for about 15 minutes until golden brown. Let cool.
How to make the frosting:
1.In a bowl of a stand mixer, or with a hand mixer, beat the cream cheese until smooth. Add the butter and beat again until smooth.
2.While you keep beating, sift the powdered sugar into the cream cheese mix.
3.Add vanilla sugar and lemon juice and beat until smooth.
4.Either spread the frosting onto the cupcakes with a knife or use a large open star decorating tip to pipe the frosting.