Preheat your oven to 375°F (190°C) and line two baking sheets with parchment paper.

In a microwave-safe bowl, combine half a cup of semi-sweet baking chocolate with a stick of diced unsalted butter and melt in 30-second increments.

Sift together 1.25 cups of all-purpose flour, 1 teaspoon of baking powder, 0.5 teaspoon of salt, and 0.33 cup of Dutch-process cocoa powder in a large bowl.

In a stand mixer, beat together 2 large eggs with 1 cup of light brown sugar, 1 teaspoon of vanilla extract, and 0.5 teaspoon of peppermint extract until well combined.

Slow the mixer and gradually add the melted chocolate mixture to the egg and sugar mixture until thoroughly blended.

Gradually mix the dry ingredients into the wet mixture using a spatula, and fold in 1 cup of chocolate chunks.

Wrap the cookie dough tightly in plastic wrap and chill in the refrigerator for at least 30 minutes.

Scoop tablespoon-sized portions of dough and roll them into balls, placing them on the lined baking sheets.

Bake the cookies for approximately 9 minutes or until slightly undercooked in the center.

Press half of a large marshmallow onto each cookie and return to the oven for an additional 2-3 minutes.

Transfer cookies to a wire rack to cool slightly, then drizzle melted chocolate and sprinkle with crushed peppermint candy.