– 10 tablespoons (142 grams) unsalted butter – Adds fudgy richness and soft texture.

– 1 cup (200 grams) granulated sugar – Sweetens and helps create the brownie structure.

– 1/3 cup (67 grams) packed light brown sugar – Adds moisture and a deeper caramel-like flavor.

– 3/4 cup plus 2 tablespoons (88 grams) unsweetened cocoa powder, sifted – Delivers that classic chocolate taste and color.

– 1/2 teaspoon vanilla extract – Rounds out flavor and boosts the chocolate aroma.

– 2 large eggs plus 1 egg yolk – Creates chewy fudginess and a tender center.

– 1 tablespoon corn syrup – Contributes to chew and helps the brownies stay soft.

– 2/3 cup (85 grams) all-purpose flour – Gives just enough structure without drying the brownies out.

– 1 tablespoon cornstarch – Helps with the thick, tender crumb and signature chew.

– 1/4 teaspoon fine sea salt – Balances sweetness and makes chocolate taste fuller.

– 1/2 cup heavy cream – Creates a smooth, pourable chocolate frosting.

– 1 1/2 cups (255 grams) semisweet chocolate chips – The base for that shiny, set frosting layer.

– Rainbow candy-coated chocolate chips, mini chocolate candies, sprinkles, or other candy for topping – Gives the classic cosmic look.