Preheat oven to 350 degrees.
Place oats in blender and blend until fairly smooth. Mix together with baking soda and set aside.
Cream peanut butter, butter and sugars together until smooth. Add in egg and vanilla, beating until smooth.
Stir in oats. Add in chocolate chips and mix until just combined.
In a 9 inch springform pan, or pizza pan, spread out dough evenly, leaving a 1/2 inch border around edges of pan.
Bake for 18-20 minutes until center is set.
Allow to cool.
For the frosting:
Beat together the butter and peanut butter and add in powdered sugar slowly.Be sure your powdered sugar is sifted to prevent clumps in your icing. Add 1 tablespoon of milk at a time, to thin icing to desired consistency.
Pipe out frosting along edges or to spell out Happy Birthday.
You will have extra frosting--I recommend eating it with a spoon :)