Preheat your oven to 160C Fan/180C/350F/Gas Mark 4 and line a cupcake tin with black cupcake cases.
In a mixing bowl, whisk together the softened butter and caster sugar until light and fluffy.
Add in the large eggs along with vanilla extract, mixing well until fully incorporated.
Gradually mix in buttermilk, cocoa powder, bicarbonate of soda, red food coloring, and self-raising flour until well combined.
Divide your batter evenly among the prepared cupcake cases and bake for about 20-25 minutes or until a skewer comes out clean.
Once cooled, core each cupcake to fill them with jam and whip up your buttercream using softened butter, icing sugar, milk, vanilla extract, and pink food coloring.