Preheat your oven to 180°C (160°C fan). Line a 12-hole muffin tin with paper cases. The kitchen should be warming up nicely now, and you'll smell the faintest hint of warmth as the oven comes to temperature.

Combine the dry ingredients. In a large mixing bowl, sift together the flour, sugar, cocoa powder, baking powder, bicarbonate of soda, and salt. Whisk them until they're a uniform, deep brown colour — you shouldn't see any streaks of white flour remaining. The cocoa will release its rich, earthy aroma as you work.

Add the wet ingredients. Make a well in the centre and crack in the eggs. Pour in the milk, vegetable oil, and vanilla extract. Whisk gently at first, then increase speed until the batter is smooth and glossy. It should look like thick, dark chocolate sauce and smell intensely of vanilla.

Pour in the boiling water. This is the magic step. Slowly stream in the boiling water while whisking continuously. The batter will become thin and watery — almost like a milkshake. Don't panic; this is correct. The mixture should have a silky, pourable consistency.

Fill the cases. Divide the batter evenly among the 12 paper cases, filling each about two-thirds full. The batter will look very liquid in the cases, but it will set beautifully in the oven.

Bake for 18-20 minutes. Place the tin in the centre of the oven. After 15 minutes, check them — the tops should spring back when lightly touched, and a skewer inserted into the centre should come out clean or with a few moist crumbs. The kitchen will smell like a chocolate factory at this point. Cool in the tin for 5 minutes, then transfer to a wire rack to cool completely. You should hear a faint crackle as the cupcakes release from the paper cases.

Make the buttercream. While the cupcakes cool, beat the softened butter in a clean bowl until pale and fluffy — about 3 minutes. It should look like thick cream and feel light and airy. Gradually add the sifted icing sugar, one spoonful at a time, beating well after each addition. Add the milk and beat for another 2 minutes until the buttercream is smooth, spreadable, and the colour of pale ivory.

Decorate. Once the cupcakes are completely cool (this is crucial — warm cupcakes will melt your buttercream into a sad puddle), pipe or spread the buttercream on top. Finish with a generous scattering of red and green sprinkles. The contrast of the dark chocolate sponge against the white buttercream and bright sprinkles is pure Christmas cheer.