1. Preheat the oven to 350°F.
2. Lightly spray a 9-inch square baking pan with cooking spray. Line it with parchment paper, leaving an overhang for easy removal. Set aside.

Brownies

1. In a large bowl, combine the chocolate chips and butter. Melt in the microwave on high in 30-second increments, stirring in between.
2. Stir in the sugar and vanilla extract until completely combined.
3. Add the eggs one at a time, stirring in between each addition until combined.
4. In a small bowl, whisk together the cocoa powder, cornstarch, and salt.
5. Add the dry mixture to the wet mixture and stir vigorously until smooth and beginning to pull away from the sides of the bowl. This will take one or two minutes.
6. Stir in the mini chocolate chips.
7. Pour two-thirds of the brownie batter into the prepared pan and smooth the top with a spatula. Set aside.

Cheesecake Layer

1. Using a stand mixer or hand-held mixer, beat the cream cheese until light and fluffy.
2. Add the sugar and beat until combined.
3. Beat in the egg and vanilla extract until smooth.
4. Spoon the cheesecake filling over the brownie batter and carefully spread it into a thin layer with an offset spatula.
5. Drizzle or spoon the remaining brownie batter over the top.
6. Bake for 30 to 35 minutes, or until an inserted toothpick comes out with a few moist crumbs. Watch closely after 30 minutes and rely on the toothpick test rather than the baking time alone.
7. Let the brownies cool completely in the pan. Use the parchment paper overhang to lift them out, then cut into squares.
8. Store in an airtight container in the refrigerator.