The basic muffin recipe I use is really simple, I just throw in the flavours I fancy/have to hand.
250g (9 oz) Plain Flour
150g (5oz) Caster Sugar
3 Teaspoons of Baking Powder
1/2 Teaspoon of Salt
225ml (8 fl oz) Semi-skimmed Milk
4 Tablespoons of Vegetable Oil
Additional flavour ingredients as required
Preheat the oven to 200 C/Gas 4
Place all the dry ingredients into a mixing bowl. Stir, then make a well in the middle.
In another bowl beat the egg and add the remaining wet ingredients.
Add the wet ingredients to the well in the dry bowl and quickly mix the two together with a fork (but don't beat). Then add the flavours (in my case it was one ripe mashed banana and approx 100g of dark chocolate broken into small chunks) and stir. Divide into muffin paper cases/tin. Bake for 20-25 minutes till golden brown.
Other possible flavours I've used are:
Coffee & Chocolate
Apple & Cinnamon
This recipe can also be made into a savoury muffin by putting half the sugar in and adding grated cheese & chives or perhaps cooked bacon & onions.