Preheat the oven to 190°C (170°C Fan, Gas Mark 5). Line a muffin tray with 12 cupcake cases. In a mixing bowl, beat the margarine with the sugar until pale and creamy-light in texture. Stir in the Vanilla Extract.
Gradually whisk in the eggs, then sift the flour, Cocoa and Baking Powder on top. Add the Chocolate Chips and using a large metal spoon, carefully fold the dry ingredients into the eggy mixture.
Spoon into the cupcake cases and bake on the middle shelf in the oven for 16-18 minutes until risen and just firm to the touch. Transfer to a wire rack to cool.
For the ganache, place the cream and Peppermint Extract in a pan and gently heat until the cream is just boiling. Pour the cream over the chocolate, leave for stand for a minute then mix until all the chocolate has melted. Place in the fridge to cool, once cooled whip the ganache with an electric whisk until a pipe-able consistency.
Place the ganache into a piping bag fitted with an open star nozzle. Pipe a large ganache swirl onto each cupcake. Sprinkle the Chocolate Sprinkles over the cupcakes and your cupcakes are now ready to serve! Store in the fridge if you are not serving them straight away.