Preheat oven to 350 degrees Fahrenheit, and either line a 9-inch square baking pan with parchment paper, or grease it with butter or vegetable oil.
Brownies
Melt chocolate along with butter in a double boiler and allow it to cool. You can also melt chocolate in a heat proof bowl over a pot of simmering water, but make sure that bottom of bowl does not touch the water.
Beat eggs and sugar for 2 minutes until pale yellow.
Slowly mix in the flour.
Thoroughly blend in the cooled melted chocolate.
Spread batter evenly in the prepared pan and freeze it for 10 minutes.
Cheesecake
Process all ingredients for cheesecake in a food processor for 1 minute.
Gently pour cheesecake mixture over the cool brownie layer. Be careful not to mix these two layers together.
Bake for about 1 hour, until a toothpick inserted near the center comes out with only a few moist crumbs.