Ingredients:

  • 1 cup unsalted butter, softened
  • 3/4 cup granulated sugar
  • 1/2 cup light brown sugar, packed
  • 2 large eggs, room temperature
  • 1 tablespoon vanilla extract
  • 2 1/2 cups all-purpose flour, spooned and leveled
  • 1 teaspoon baking powder
  • 1/2 teaspoon baking soda
  • 1 teaspoon fine sea salt
  • 1 1/2 cups plain or peanut M&M's, divided

Instructions:

  1. Preheat your oven to 350°F (175°C). Line the 9x13 inch pan with parchment paper, ensuring the paper hangs over the long sides to create 'slings' for easy removal. Lightly grease any exposed pan edges.
  2. Whisk together the flour, baking powder, baking soda, and salt in a medium bowl. Set aside.
  3. In the bowl of your mixer, beat the softened butter, granulated sugar, and brown sugar on medium speed until the mixture is light, pale, and fluffy (about 3–4 minutes).
  4. Reduce the speed to low. Add the eggs one at a time, mixing well after each addition. Scrape down the sides of the bowl. Stir in the vanilla extract.
  5. Gradually add the dry mixture to the wet mixture, mixing only until just combined. Stop immediately when the last streaks of flour disappear (overmixing leads to tough bars).
  6. Gently fold in 1 cup (2/3rds) of the M&M’s by hand using a spatula.
  7. Transfer the thick cookie dough into the prepared pan. Using your hands or the bottom of a measuring cup, press the dough evenly into all corners.
  8. Sprinkle the remaining ½ cup of M&M’s evenly over the top of the dough. Gently press them in slightly so they adhere.
  9. Bake for 28 to 30 minutes. The bars are ready when the edges are set and lightly golden brown, but the centre still looks slightly pale and soft—this ensures a wonderfully chewy texture.
  10. Remove the pan from the oven. Allow the bars to cool completely in the pan on a wire rack for at least 60 minutes before attempting to cut them.
  11. Use the parchment paper sling to lift the entire slab out of the pan. Place on a cutting board and cut into 18 squares. Serve at room temperature.