Peanut butter is used three times in these dense, rich, moist, fast, and easy bars. There’s peanut butter stirred into the dough, Peanut Butter M&Ms, and peanut butter chips, so the bars pack a bold, peanut buttery punch. There’s plenty of chocolate, the perfect compliment to all that peanut butter. Use the dough base as a blank canvas and start cleaning out your pantry – butterscotch or white chocolate chips, nuts and seeds, dice old holiday candy and toss it in. Mix and match with the add-ins you have on hand rather than buying new. Cleaning out your pantry never tasted so good.
Preheat oven to 350F. Line an 8-by-8-inch baking pan with aluminum foil, spray with cooking spray; set aside.
In a large, microwave-safe bowl melt the butter, about 1 minute on high power.
Wait momentarily before adding the egg so you don’t scramble it. Add the egg, brown sugar, vanilla, and whisk until smooth.
Add the peanut butter and whisk or stir until smooth and incorporated.
Add the flour and stir until just combined, don’t overmix.
Add all remaining add-ins and fold to incorporate.
Turn batter out into prepared pan, smoothing the top lightly with a spatula. I like to strategically place a few M&Ms on the top of the batter for a nice visual effect.
Bake for about 25 minutes, or until top is set. A toothpick inserted in the center should come out clean, or with a few moist crumbs, but no batter. Allow bars to cool in pan for at least 30 minutes before slicing and serving. Bars will keep airtight at room temperature for up to 1 week, or in the freezer for up to 6 months.