Preheat the oven to 350°F (or 325°F for a convection oven). Grease an 8x8-inch square pan with spray oil and line with parchment paper. Avoid using a glass pan.

In a large bowl, combine the butter and chocolate. Melt in the microwave in 15 to 30-second increments, stirring until fully melted. Alternatively, melt over a double boiler.

Add the granulated sugar and whisk until combined.

Add the eggs one at a time, whisking until fully incorporated after each addition. Add the vanilla with the last egg and whisk to combine.

Sift together the flour and cocoa powder, then add to the bowl along with the Oreo crumbs and salt. Stir to combine.

Fold in the chopped Oreos and chopped chocolate or chocolate chips.

In a large bowl, combine the white chocolate and butter. Melt in the microwave in 15 to 30-second increments, stirring until fully melted. Alternatively, melt over a double boiler.

Add the granulated sugar and whisk until combined.

Add the egg and vanilla extract, mixing well.

Stir in the flour and salt until combined.

Fold in the chopped Oreos.

Pour half of the chocolate batter into the prepared pan and smooth with a spatula.

Pour the white batter on top and spread evenly.

Top with the remaining chocolate batter, spreading gently to avoid mixing the layers.

If desired, sprinkle with extra chopped Oreos.

Bake for about 40 minutes, until the edges are set and a toothpick inserted in the center comes out clean.

Let the brownies cool before slicing and serving.

- Store brownies in an airtight container at room temperature for up to 2 days, or in the fridge for up to 6 days. Allow them to come to room temperature before serving.

- You can also freeze the brownies for up to 2 months. Thaw in the fridge overnight.