Preheat oven to 350°F. Spray a 9×13 baking pan with non-stick spray and line with parchment, leaving 2 inches overhang on the sides for easy removal.

In a stand mixer fitted with a paddle attachment, beat butter and sugar until light and fluffy.

Mix in cooled chocolate, vanilla, and eggs until just combined, scraping the bowl as needed.

Add flour and baking powder, mixing until no dry streaks remain.

Spread half the batter in the pan. Arrange about 24 Oreos in a single layer over the batter.

Spread the remaining batter over the Oreos, smoothing evenly. Top with about 6–7 crushed Oreos, pressing lightly into the surface.

Bake 30–35 minutes, or until a toothpick inserted 2 inches from the edge comes out with moist crumbs.

Cool completely on a wire rack before slicing. Store in an airtight container up to 3 days.