Preheat the oven to 220°C and grease two baking trays.
Heat 55g butter and 150ml water in a pan until melted and boiling.
Remove from heat, add 65g flour, and beat into a soft ball.
Return to heat and beat for one minute before cooling slightly.
Gradually whisk in 2 beaten eggs until the mixture is smooth and pipeable.
Pipe 20 mounds onto trays and flick with water to create steam.
Bake at 220°C for 10 minutes, then at 190°C for 10 more minutes.
Pierce the bottom of each bun and cool on a wire rack.
Bring 250ml milk and vanilla to a boil, then cool for 30 seconds.
Whisk egg yolks, sugar, cornflour, and 10g flour together.
Whisk hot milk into the egg mixture and return to the pan.
Boil and whisk until thickened, then stir in red food colouring.
Cover with film and chill the cream in the fridge.
Melt chocolate, 30g butter, and 4 tablespoons of water over simmering water.
Beat in 150g icing sugar until the mixture is smooth.
Pipe the cream into cold buns and dip the tops in chocolate icing.