Preheat your oven to 350°F (175°C) and coat an 8-inch square baking pan with cooking spray.

In a small bowl, combine ½ cup of granulated sugar with ¼ cup of unsweetened cocoa powder and set aside.

In a large mixing bowl, whisk together 1 cup of all-purpose flour, ¾ cup of granulated sugar, ½ cup of cocoa powder, 2 teaspoons of baking powder, and a pinch of salt.

In a medium bowl, whisk together 1 cup of milk, ¼ cup of melted unsalted butter, 1 egg yolk, and 1 teaspoon of vanilla extract.

Fold the wet ingredients into the dry ingredients gently, then add 1 cup of semisweet chocolate chips.

Spread the batter evenly in the prepared pan, then sprinkle the reserved cocoa mixture over the top.

Carefully pour 1 and ¾ cups of boiling water over the batter without stirring.

Bake for 22 to 24 minutes until the top is cracked and a toothpick comes out mostly clean.

Let it cool for about 10 minutes before serving warm, ideally with vanilla ice cream.