Pre-heat oven to 350 degrees. Spray pizza pan with Baker's Joy or line a cookie sheet with parchment.
Melt butter, shortening, and peanut butter in the microwave for about 30-45 seconds. Stir in brown sugar and granulated sugar. (This is a good time to sample a little batter because butter, peanut butter and sugar mixed together taste awesome and we haven’t put the egg in yet
Stir in egg and vanilla. Stir in baking soda and flour. The dough should be fairly thick.
Plop dough on ungreased pizza pan or cookie sheet. Spread to the edges of the pan. I often find it easier to push the dough to the edges with my hands. The dough may not fill up your pizza pan. The pan I had growing up was perfect, but the one I have now, the dough does not quite reach the edges. That is ok.
Bake at 350 degrees for 15 minutes. Don’t go a lot longer. You want a soft cookie base. Immediately after removing from the oven pour chocolate chips. Do not move them around if you can help it, they will be kind of melty. If you accidentally pour them all on one spot, just spread them across the top like frosting. It will be a different look, but taste the same.
If you want to get crazy and put marshmallows on top, add 1/2 cup mini marshmallows immediately after the chocolate chips. Place back in the oven on the top rack for a few minutes to brown the marshmallows. (Or use a kitchen torch.)
If you don't want to use shortening, I've used all butter for this recipe and had good luck, it will just be a little crispier but more buttery!