For the Chocolate Cupcakes:

• 1 cup (125g) all-purpose flour
• 1/2 cup (45g) unsweetened cocoa powder
• 1 teaspoon baking soda
• 1/2 teaspoon baking powder
• 1/4 teaspoon salt
• 1/2 cup (113g) unsalted butter, softened
• 3/4 cup (150g) granulated sugar
• 1 large egg
• 1 teaspoon vanilla extract
• 1/2 cup (120ml) buttermilk
• 1/2 cup (120ml) hot coffee or hot water

For the Gooey Chocolate Filling:

• 1/2 cup (120g) semi-sweet chocolate chips
• 1/4 cup (60ml) heavy cream
• 1/4 cup (65g) creamy peanut butter or Nutella (optional for extra richness)

For the Marshmallow Meringue Frosting:

• 3 large egg whites
• 3/4 cup (150g) granulated sugar
• 1/2 teaspoon cream of tartar
• 1 teaspoon vanilla extract

For Garnish:

• Graham cracker crumbs or mini graham crackers
• Chocolate drizzle (optional)