Preheat the oven to 375°F.

Grease a 2-quart baking dish with butter.

In a double boiler, melt the chocolate and butter together. Stir until smooth and set aside to cool.

In a large bowl, combine the egg whites, cream of tartar, and a pinch of salt. Whisk until the mixture is glossy and forms stiff peaks.

In a separate bowl, combine the sugar, cocoa powder, and vanilla. Slowly add the melted chocolate mixture and whisk until combined.

Using a rubber spatula, gently fold the egg whites into the chocolate mixture until fully incorporated.

Pour the batter into the greased baking dish and bake for 20-25 minutes or until the soufflé is fully risen and the top is golden brown.

Serve with a dollop of fresh cream and enjoy!