Mocha mint chip cupcakes

Ingredients

• 1/2 tablespoon instant coffee granules
• 1/4 cup just-boiled water
• 125 grams butter, softened
• 1/2 cup caster sugar
• 2 eggs
• 1 1/2 cup self-raising flour
• 2 tablespoons cocoa powder
• 1/3 cup milk
• 2 50g peppermint crisp bars, chopped, plus 1 extra to serve
• Butter cream
• 125 grams softened butter
• 1/2 teaspoon peppermint essence
• 1 1/4 cup icing sugar, sifted
• 1/4 cup cocoa powder, sifted
• 2 tablespoons milk