Step 1: Preheat and prepare the baking dish
Preheat your oven to 325°F (163°C). Butter a 2-quart oval or rectangular baking dish.
Step 2: Melt the butter
In a small saucepan or microwave-safe bowl, melt the butter and set aside to cool slightly.
Step 3: Beat the eggs and sugar
In the bowl of a stand mixer fitted with the paddle attachment (or use a hand mixer), beat the eggs and sugar together on medium-high speed for 5–10 minutes, until thick and pale yellow.
Step 4: Add remaining ingredients
Reduce the mixer speed to low and add the cocoa powder, flour, vanilla extract, and the melted butter. Mix until just combined—do not overmix.
Step 5: Pour into dish and prepare water bath
Pour the batter into the prepared baking dish. Place the dish inside a larger roasting pan and add enough hot tap water to the pan to come halfway up the sides of the baking dish.
Step 6: Bake the pudding
Bake for exactly 1 hour. The top will form a crisp crust, but the inside will remain soft and gooey.
Step 7: Cool slightly and serve
Let sit for 10–15 minutes before serving. Scoop out portions with a spoon and serve warm with vanilla ice cream or whipped cream.
