Preheat your oven to 350°F and prepare a 9x9 baking pan by lining it with parchment paper or lightly greasing it.

In a small saucepan over low heat, gently melt the butter with the dark chocolate chips until smooth and luscious, stirring frequently to combine. Allow it to cool slightly.

For the cheesecake layer, beat the cream cheese until velvety smooth. Gradually add in the sugar and continue beating until well combined, then incorporate the egg white, red velvet extract, and vanilla extract until the mixture is creamy and vibrant. Set aside.

For the brownie base, beat together the eggs, egg yolk, brown sugar, granulated sugar, and vanilla extract until the mixture is thick and frothy. Slowly pour in the cooled chocolate mixture while the mixer is on low, blending until completely smooth.

Fold the cocoa powder, salt, and whole wheat pastry flour into the wet ingredients until just combined.

Pour most of the brownie batter into the prepared pan, spreading it evenly to the edges. Top with the red velvet cheesecake layer, smoothing gently. Dollop the reserved brownie batter on top, then swirl through with a knife for a marbled effect.

Bake in the preheated oven for 30-35 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs. Let cool completely, then slice into 16 brownies and enjoy!