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Monster Cookie Bars

Monster Cookie Bars

These Monster Cookie Bars are chewy, oat-forward peanut-butter bars studded with M&Ms and chocolate chips for pockets of chocolate and crunch. Chill the slab before baking for clean slices; they bake in about 35 minutes and are perfect for Halloween treats, bake sales, or lunchboxes.
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Cook Time:35 minutes
Total Time:4 minutes
Course: Desserts
Keyword: Halloween, oats, peanut butter

Equipment

  • 8-by-8-inch baking pan
  • parchment paper
  • stand mixer or mixing bowl
  • paddle attachment (optional)
  • rubber spatula
  • wire rack

Ingredients

  • 1/2 cup unsalted butter 113g (1 stick), at room temperature
  • 1 cup light brown sugar 210g, packed
  • 1/2 cup creamy peanut butter 140g, at room temperature
  • 1 teaspoon honey
  • 1 1/2 teaspoons vanilla extract
  • 1 large egg at room temperature
  • 1 large egg yolk at room temperature
  • 1 cup all-purpose flour 125g
  • 1/4 teaspoon fine sea salt
  • 1/4 teaspoon baking soda
  • 1 1/2 cups old-fashioned rolled oats 150g
  • 1/2 cup M&Ms candies 100g
  • 1/2 cup chocolate chips 90g
  • candy eyeballs for topping (optional)

Instructions

  1. Lightly butter the bottom and sides of an 8-by-8-inch baking pan, then line the pan with parchment paper so it stays in place.
  2. In a mixing bowl or the bowl of a stand mixer fitted with the paddle attachment, beat the butter, packed light brown sugar, creamy peanut butter, honey, and vanilla until the mixture is fluffy and slightly lighter in color.
  3. Scrape down the sides of the bowl, then add the egg and egg yolk and mix until fully incorporated.
  4. Add the all-purpose flour, fine sea salt, and baking soda and mix on low speed until nearly incorporated. Add the rolled oats and mix briefly to distribute, then fold in the M&Ms and chocolate chips with a rubber spatula, scraping any dry bits from the bottom and sides of the bowl.
  5. Transfer the dough to the prepared pan and use a spatula to press it evenly to the edges. Cover and chill for at least 2 hours or up to overnight.
  6. Preheat the oven to 350 degrees F and let the chilled pan sit at room temperature briefly while the oven preheats.
  7. Bake for 33 to 37 minutes, until the top is puffed and no longer raw-looking and the edges are just starting to brown.
  8. Remove the pan from the oven and set it on a wire rack to cool. When cool enough, lift the slab out using the parchment and place it on the rack to cool completely before slicing into squares. Store leftover bars refrigerated in an airtight container for up to 5 days.

Notes

Chill the assembled dough at least 2 hours or overnight for the cleanest slices. Let the chilled pan warm slightly while the oven preheats so the slab bakes evenly. Store bars refrigerated in an airtight container for up to 5 days; top with candy eyeballs for a Halloween look if desired.