Preheat the oven to 350 degrees F (180 degrees C) and spray an 8x8-inch dish with
Nonstick Cooking Spray (as needed)
Salted Butter (1/2 Tbsp)
Chunky Peanut Butter (1/2 cup)
in a large, microwave-safe bowl. Heat in a microwave oven for 30 seconds, then stir together. Microwave another 30 seconds and stir some more, until completely melted.
Stir in the
Dark Brown Sugar (1 1/2 cups)
Vanilla Extract (1 Tbsp)
. Slowly add in the
All-Purpose Flour (2 cups)
Baking Powder (1 tsp)
Ground Cinnamon (1/2 tsp)
. Fold in the
Semi-Sweet Chocolate Chips (1 cup)
Spread the batter into an even layer in the prepared baking dish and bake it for 40-45 minutes. The top should be dry and starting to crisp up around the edges, while the center will still be slightly gooey.
Let them cool completely, then cut into 16 squares by making 3 equal cuts both vertically and horizontally. Serve them immediately or store in an airtight container for up to 3 days.