Cupcakes are super simple. Basically you use the same amount of butter (or baking spread), caster sugar and flour and then tailor the number of eggs depending how much of the other dry stuff you have e.g. if I use 150g of flour, etc I would use 2 eggs, if 200g I'd use 3 eggs.
You can get a general idea of amounts of other ingredients to use by weighing the eggs (in their shells) and then matching the amount in sugar, flour, butter.
Today I only wanted to make 6 cupcakes to use up icing so I weighed 1 egg and it was about 65g so I weighed out 65g each of flour, baking spread and sugar. Whisk sugar and butter/spread together. Add the egg, ½ teaspoon of vanilla and mix. Add flour, ½ a teaspoon of baking powder and a splash of milk if required and mix.
Put into cases in a cupcake tin and cook for 18-20 minutes.
I wanted to play with a flower nozzle today for the 1st time and used up my spare frosting to do so.