Heat the oven to 350°F. Grease the bottom and sides of a rectangular pan, 13x9x2 inches, with shortening or non-stick spray.
Melt the chocolate and butter in a 1-quart saucepan over low heat, stirring frequently. Let it cool.
Beat the cream cheese filling ingredients together until smooth and set aside.
Beat together the cooled chocolate mixture, sugar, vanilla and eggs in a large bowl with an electric mixer on medium speed for 1 minute, scraping the bowl occasionally.
Beat in the flour and salt on low speed for 30 seconds, scraping the bowl occasionally. Beat on medium speed for 1 minute. Stir in the nuts. Spread half of the batter (2 1/2 cups) in the pan. Spread the cheesecake filling over the batter. Carefully spread the remaining brownie batter over the cream cheese filling.
You can bake it as is or create the pretty design you see in the picture. To do that, take a butter knife and insert it into the layers of batter. Swirl the knife a bit so that the batters mix just a bit into a swirl pattern as in the image.
Bake in an oven preheated to 350°F for 45-50 minutes or until a toothpick inserted in the center comes out clean. Cool the cheesecake brownies in the pan on a wire rack.