Preheat the oven to 325F, and line a 9x9 baking pan with parchment or foil that's been sprayed with nonstick spray. This is really important!

In a medium bowl, prepare brownies according to package directions.

Pour batter into prepared pan and bake for about 30 minutes. It's okay if they're still a little soft!

In another medium bowl, using a mixer, beat together the cream cheese, sour cream, vanilla, and sugar until fluffy and lump-free.

Add in the eggs, one at a time, beating well after each addition.

Add in ¾ of the crushed Oreos, and beat with the mixer {this will help crush them up more!}

When the brownies are cooked, remove from oven, pour the cheesecake layer on top, and sprinkle the remaining Oreos on top.

Return pan to oven, and bake for 40 minutes longer. Cheesecake should only be slightly jiggly in the center, if at all!

Remove from oven, and let them cool to room temperature, then refrigerate overnight. I mean it!

Once they are chilled, remove from the pan using the parchment or foil, and cut into 9 even squares. Store leftovers in the fridge!