Line an 8x8 or 9x9 inch baking pan with foil long enough to hang over on two sides, making it easier to remove from pan once baked. Spray pan and foil.
In microwave, melt butter and chocolate in a microwave safe bowl, until smooth (stir every 30 seconds).
In a separate bowl, beat eggs, and vanilla with the sugar. Slowly add in the chocolate mixture until well combined.
In small bowl, sift together cocoa, salt and flour. Add mixture to rest of batter. Do not over mix.
Pour batter into prepared baking pan.
Cheesecake Layer
Beat ingredients together until smooth. Pour over brownie batter. Using a sharp knife, slowly swirl together the layers slightly.
Bake 1 hour to 1 hour 10 minutes, or until just set and toothpick inserted comes out clean. Cool before eating.