Preheat your oven to 425°F (218°C) and prepare your skull cake pan by greasing with unsalted butter and dusting with flour.

In a heatproof bowl, melt unsalted butter and semisweet chocolate together until smooth.

In a separate bowl, whisk eggs and sugar until pale and thick, about 3-4 minutes, then add vanilla extract, cocoa powder, and food coloring.

Gently fold the melted chocolate mixture into the egg mixture, then sift in flour and mix until just combined.

Spoon the batter into molds, filling them about three-quarters full, and smooth the tops.

Bake for 11-13 minutes until edges are set but centers remain soft and slightly jiggly.

Let cakes cool in the pan for about 5 minutes, then invert onto a wire rack to cool completely.

For the glaze, whisk together the glaze ingredients until smooth and drizzle over the unmolded cakes.