1. Preheat the oven to 350 degrees F. Grease a 9x13 inch baking dish.

2. In a large mixing bowl, beat together the butter, brown sugar and sugar until combined.
Add the eggs, one at a time, beating until combined and creamy.
Beat in the vanilla.
Add the flour, and baking soda, beat until combined.
Stir in the the chocolate chips.

3. Spread 1/2 the dough out in the prepared dish.
Dollop and then gently swirl the peanut butter into the dough.
Add the remaining dough over top, don't worry if the dough doesn't fully cover the peanut butter.
Transfer to the oven and bake for 20-22 minutes, until just set in the center.
Let cool and then cut into bars.
Store for up to 5 days in an airtight container.