Preheat your oven to 350°F (175°C) and prepare an 8×8 inch baking pan with parchment paper.

Melt the butter in a saucepan over low heat, then mix in the granulated sugar, brown sugar, and cocoa powder until glossy.

Remove from heat, cool slightly, and whisk in eggs one at a time along with vanilla extract.

Gently fold in flour and baking powder until just combined; avoid over-mixing.

Pour the batter into the prepared pan, spread evenly, and bake for 25-30 minutes or until a toothpick comes out with a few moist crumbs.

Allow to cool before cutting into heart shapes.