Vegan cupcakes with banana peanut butter

Name: Vegan cupcakes with banana & peanut butter
Ingredients: 240g self-raising flour; 140g golden caster sugar; 1 tsp bicarbonate of soda; 240g egg-free mayonnaise; 2 large or 3 small ripe bananas, mashed; 1 tsp vanilla extract; 25g vegan dark chocolate chip; 80g vegan margarine; 250g icing sugar; 25ml vegan milk (we used almond milk); 2 tbsp smooth peanut butter