I make many many cupcakes - and honestly the best recipe ever which works every time is a nigella one for fairy cakes which is in her how to be a domestic goddess book (page 40).
Fairy Cakes: Nigella's How To Eat
Ingredients
125 grams Self-raising flour
125 grams Unsalted butter, soft
125 grams Caster Sugar
2 Eggs
2 teaspoons Vanilla Extract
1 teaspoon Baking powder
Milk
Method
1.Throw all the ingredients in a food processor except the milk.
2.Leave to blend for a few mins until its all mixed together, then drip in a few teaspoons of milk, so it becomes more of a cake batter consistency.
3.Put into cases, bake at 200°C for about 10/15 mins (until they look nicely brown, and a skewer comes out clean)
Personally for my oven I set it at 180 fan. The mix I find makes about 9-12 cupcakes (rather than smaller fairy cakes). They can be frozen as well.
I have honestly make these about 1000 times (I do bake semi professionally) and they have never not worked.
For the icing, I always do a butter icing. Double the amount of icing sugar per butter. For chocolate you use cocoa powder - good quality and maybe about 50g per 200g icing sugar? I used to blend in real melted chocolate but honestly I find good quality cocoa powder to be the best.
You can also add a bit of philadelphia soft cheese to butter cream to make it less sweet, not too much as it then looses it's stiffness and doesn't pipe too well.
Also for cupcakes I like to core out the middle with an apple corer and add other things, like caramel, raspberry Jam or curds (passion fruit or lemon). Obviously the icing colour and type needs to match the middle addition.
Good luck!