Preheat your oven to 325°F (163°C). Lightly grease an 8-inch square baking dish with butter or nonstick spray.

In a small saucepan over low heat, melt the butter gently. Do not brown it. You want it fully melted and smooth. Set it aside to cool slightly.

In a large mixing bowl, beat the eggs and sugar together using a hand mixer on medium-high speed for about 5–10 minutes. This step is important. The mixture should become thick, pale, and fluffy. You’re incorporating air, which helps create that signature top layer.

Slowly pour the slightly cooled melted butter into the egg mixture while mixing on low speed. Add the vanilla extract and mix until combined.

In a separate bowl, whisk together the cocoa powder, flour, and salt. This ensures even distribution.

Gently fold the dry ingredients into the wet mixture using a spatula. Do not overmix. Stir just until everything is incorporated and the batter looks smooth and glossy.

Pour the batter into the prepared baking dish and smooth the top. Bake for 35–40 minutes.

The top should look set and slightly cracked, but the center will still be soft. That softness is exactly what you want.

Let it cool for about 10–15 minutes before serving. Scoop into bowls while warm.