To make the cookie dough base:

With mixer set to high speed, beat butter and brown sugar in a large mixing bowl until creamy. Add vanilla, peanut butter, and condensed milk, mix until combined.

Slowly, add in the flour until combined. Then gently fold in the chocolate chips.

Line a 8x8 baking dish with plastic wrap or foil. Press the cookie dough mixture into the baking dish.

To make the chocolate peanut butter ganache topping:

Add chocolate chips and peanut butter to a microwave safe bowl. Heat in the microwave for 30 seconds, then stir until all chocolate has melted. Heat in increments of 15 seconds if the chocolate hasn't melted.

Pour the topping over the cookie dough and spread with a spatula.

Place the baking dish in the fridge for 3 hours, or overnight, until fully set. Then, cut into mini bite sized bars.

Keep any left over bars refrigerated in an airtight container for up to a week.