Step 1

Separate 4 large eggs. Pour egg yolks into a medium-size bowl, reserve egg whites for later. TIP: See the notes for leftover egg white recipe ideas.

Step 2

Into a bowl with egg yolks add granulated sugar (1cup, 200grams), then pour in flour (3 tablespoons, 45grams), corn starch ( (3 tablespoons, 45grams), dark cocoa powder (1/4 cup, 25grams) and salt (1/4 tsp). Pour in milk (1 cup, 240-250 ml). Whisk well, till combined. Then pour in the remaining milk (1 cup).TIP: You can use whole milk, 2% or 1% milk.

Step 3

Cook the custard on a medium-high heat until custard starts to thicken. Then add chopped dark chocolate (about 1cup, 150grams). Stirring constantly, cook the custard until it thickens. It should be thick. Cook, simmering for about 2-3 minutes, stirring constantly.

Step 4

Remove custard from the heat, push it thru a fine-mesh sieve. Cover it with a food wrap to prevent skin from forming. Let it cool to room temperature.TIP: You can speed up the cooling process by cooling custard in an ice/cold water bath.

Step 5

Cream the room temperature butter (1cup, 2 sticks, 226grams) for 1 minute. Then pour in sifted powdered sugar (1 cup and 1/2 cup,180grams). Cream for 2-3 minutes, until homogeneous, smooth and fluffy.TIP: If you are in a pinch, and need a little more buttercream up the butter by 1 stick (113grams).

Step 6

Gradually add room temperature chocolate custard to room temperature butter mixture. Beat well after each addition. Scrape down the bowl between.

Step 7

Flavor buttercream with Vanilla Extraxt (1 teaspoon) and sweet Rum (1 tablespoon, optional).Beat well, about 2 minutes. Use immediately or cover and refrigerate for up to a week, re-beat before using.