Cream together butter, sugars and vanilla. Mix in egg. Gradually blend in flour, baking soda, and salt. Spread this mixture into a large baking pan. (Don't worry about reaching the sides, this stuff grows.) Spread peanut butter on top of cookie batter. Sprinkle chocolate chips on top of peanut butter and press them in.
Bake at 350º F for 10 minutes. Swirl the chocolate and peanut butter with a butter knife. (Don't try to swirl the entire cookie like I did. Just go about halfway.) Bake for another 25 minutes. Remove from oven and let cool, then cut into squares. go back