Preheat oven to 190 degrees C. Lightly grease two 30cm pizza pans.
In a medium bowl cream together the butter, brown sugar and white sugar until smooth. Beat in the cream cheese, then the eggs one at a time, then stir in the vanilla. Combine the flour, bicarb soda and salt; gradually stir into the creamed mixture. Fold in the chocolate chips and walnuts. Divide the dough in half and press each half onto a prepared pizza pan.
Bake for 20 to 25 minutes in the preheated oven until golden at the edges. Cool completely in pans on wire racks. Cut into slices like a pizza and serve.