Preheat oven to 350 F. Grease 9 X 13 inch pan.
For crust: in a stand mixer cream butter and sugar together until fluffy. Add 2 tsp vanilla and 2 eggs one at a time, beating well after each addition. In a separate bowl, combine flour, cocoa powder, baking soda, and salt. Add to creamed butter mixture slowly until combined. Save one cup of dough for top of bars. Spread remaining dough into the bottom of the 9 x 13 pan in an even layer. Bake at 350 for 20 minutes and let cool.
For cream cheese filling: Mix together cream cheese, egg, vanilla, and powdered sugar with a stand mixer or by hand until smooth and creamy. Spread on top of cooled crust.
Drop small pieces of saved crust dough on top of cream cheese filling.
Bake at 350 F for 25-30 minutes, or until filling is set. Let cool completely before slicing. Or if you like them slightly gooey, serve while slightly warm.