Preheat the oven to 350. Butter and flour a 9x13 pan
In the bowl of a stand mixer or a large bowl with a hand mixer, beat together the eggs, cocoa, salt, baking powder, and vanilla until smooth.
In a medium pan, melt the butter. Whisk in the sugar until well-incorporated. Slowly stream the butter/sugar mixture into the egg/cocoa mixture in the bowl with the beater on medium-low until smooth. Beat in the flour, then fold in the chips. Pour into prepared pan. The batter will be thick, smooth evenly to all edges with a spoon.
for the cheesecake layer:
Beat together the sugar, cocoa, cream cheese, eggs and vanilla in the bowl of a stand mixer or medium bowl using a hand mixer until well combined. Fold in chips. Spread over the brownie layer in the pan to form an even layer.
Bake the brownies for 35 minutes, until a toothpick inserted into the center comes out clean, or with just a few moist crumbs. Cool on a wire rack before slicing.