S'mores Brownie Cupcakes

Bahan-bahan (18 porsi)

• 1 and 1/2 cups (180g) graham cracker crumbs (about 12 full-sheet graham crackers)
• 1/4 cup (50g) granulated sugar
• 6 Tablespoons (85g) unsalted butter, melted
• 1/2 cup (8 Tbsp; 113g) unsalted butter
• 2 4 -ounce quality semi-sweet chocolate bars (228g), coarsely chopped
• 1 cup (200g) granulated sugar
• 3 large eggs, at room temperature
• 1 teaspoon pure vanilla extract
• 1/2 cup (63g) all-purpose flour (spooned & leveled)
• 1/4 cup (21g) unsweetened natural or dutch-process cocoa powder
• 1/2 teaspoon salt
• 3 large egg whites, at room temperature
• 3/4 cup (150g) granulated sugar
• 1/8 teaspoon cream of tartar (do not skip!)
• 1 teaspoon pure vanilla extract