Ingredients

4 tablespoons unsalted butter, plus more for pan 

3 ounces good-quality unsweetened chocolate, coarsely chopped 

1/2 cup all-purpose flour 

1/4 teaspoon baking powder 

1/2 teaspoon salt 

1 cup sugar 

2 large eggs 

1/4 cup milk 

1 teaspoon pure vanilla extract 

4 ounces good-quality semisweet chocolate, coarsely chopped 

2/3 cup heavy cream 

Heart-shaped sprinkles, for garnish 

Preparation

Preheat oven to 325 degrees. Butter a 9-inch springform pan, and set aside.

Make batter: Put butter and chocolate in a heatproof medium bowl set over a pan of simmering water; stir until melted. Let cool slightly.

Whisk together flour, baking powder, and salt in a separate bowl; set aside.

Put sugar and eggs in the bowl of an electric mixer fitted with the whisk attachment, and beat on medium speed until pale and fluffy, about 4 minutes. Add chocolate mixture, milk, and vanilla, and beat until combined. Add flour mixture; beat, scraping down sides of bowl, until well incorporated.

Pour batter into prepared pan. Bake until a cake tester inserted into brownies (avoid center and edges) comes out with a few crumbs but is not wet, 27 to 30 minutes. Let cool completely in pan.

Make topping when brownies are cool: Put chocolate in a medium bowl. Heat cream in a small saucepan over medium-high heat until just simmering. Pour over chocolate; let stand 5 minutes. Gently stir until smooth. Allow ganache to cool, stirring every 10 minutes, until slightly thickened, 25 to 30 minutes.

Pour ganache over cooled brownies in pan; let set, about 20 minutes. Refrigerate until cold, 30 minutes to 1 hour. Let brownies stand at room temperature at least 15 minutes before serving. Lift out brownies; cut into wedges, wiping knife with a hot, damp cloth between each cut. Scatter sprinkles on top.