Preheat your oven to 350°F (175°C). Grease an 8x8-inch baking pan or line it with parchment paper for easy removal after baking.

Melt the butter in a medium saucepan over low heat. Remove from heat and stir in the granulated sugar, eggs, and vanilla extract until everything is beautifully blended.

Whisk together the cocoa powder, flour, salt, and baking powder in a separate bowl.

Combine the dry ingredients slowly into the wet mixture, stirring until just mixed.

Pour the warm brownie batter into the prepared baking pan, spreading it out evenly.

Bake in your preheated oven for 20–25 minutes. Check with a toothpick in the center.

Sprinkle the mini marshmallows, chocolate chips, and graham cracker crumbs over the top of your baked brownies immediately after they come out of the oven.

Broil the brownies for about 1–2 minutes until the marshmallows turn golden brown. Keep a close watch to avoid burning.

Cool in the pan for 10–15 minutes before serving. Drizzle with chocolate sauce if desired.

Cut into squares and enjoy warm or at room temperature.