Measure the butter into a bowl and microwave for 30-60 seconds or until fully melted. Set aside.
60 grams Unsalted butter
Measure the buttermilk into a jug and microwave for 60 seconds (don't worry if it curdles a little). The milk needs to be ~40ºC/110ºF to properly activate the yeast. No thermometer? Test the temperature by dipping your finger into the buttermilk - it should feel like warm bathwater.
250 millilitres Buttermilk
Pour the warm milk into a large bowl and sprinkle the yeast on top. Let sit for 1 minute.
1 sachet (7 grams) Fast-action dried yeast
Add the melted butter, vanilla, sugar, whole egg and egg yolk. Mix to combine (don't worry if the mixture curdles).
50 grams Caster sugar, 1 medium Egg, 1 medium Egg yolk, 2 teaspoons Vanilla extract
In a separate bowl, whisk 480g flour, cocoa powder and salt together until combined. Now add these to the bowl of wet ingredients and work the mixture into a shaggy dough.
480-500 grams Plain all-purpose flour, 40 grams Menier 100% Cocoa Powder, 1 teaspoon Salt
Transfer the dough to the bowl of an electric mixer fitted with a dough hook. Add the red food colouring.
1 teaspoon Red gel food colouring
Set the mixer to medium-low speed and knead for approx. 10 minutes. The dough is ready when it looks smooth, shiny and springs back when pressed with your finger.*If the dough sticks to the bottom of the bowl, stop the mixer and use a spatula to scrape the bottom. Sprinkle in a tablespoon of flour and turn the mixer back on. Repeat if needed until the dough comes together into a ball. ** You can also test the dough using the 'window pane' method. Tear off a piece of dough and stretch it out. If it tears, keep kneading. If it creates a thin 'window' that let's light through, it's ready. **No electric mixer? Turn the shaggy dough out onto a floured surface,add the food colouring, and knead by hand instead. Lift the dough out and lightly coat the inside of the bowl with oil. Shape the dough into a ball and place it inside the bowl. Cover with cling film.
Leave the dough to prove for 90-180 minutes in the warmest spot in your house (an airing cupboard/next to a radiator/in a sunny place). The dough should have doubled in size. It helps to take before and after pictures to compare the rise.