1. Preheat oven to 350°F (175°C) and line an 8×8-inch baking pan with parchment paper.

2. Melt butter and dark chocolate together in a double boiler or microwave, then stir in espresso powder and let cool slightly.

3. Whisk granulated sugar and brown sugar into the chocolate mixture until glossy.

4. Add eggs one at a time, whisking thoroughly, then stir in vanilla extract.

5. Sift flour, cocoa powder, salt, and baking powder together, then fold into the wet batter until just combined.

6. Pour half the batter into the pan and smooth the surface.

7. Arrange Oreo cookies in a single layer over the batter.

8. Pour remaining batter over the Oreos and spread gently to cover.

9. Sprinkle crushed peppermint candies and mini chocolate chips on top.

10. Bake for 28–32 minutes until a toothpick inserted comes out with moist crumbs.

11. Cool in the pan for at least 30 minutes, then lift out using parchment and cut into squares.

12. Store brownies in an airtight container at room temperature for up to three days