Equipment Needed
- 9×13 inch baking pan
- Parchment paper
- Large mixing bowl
- Whisk and rubber spatula
- Measuring cups and spoons
- Cooling rack
Step-by-Step Instructions
First, I always line my pan with parchment paper, leaving an overhang on the sides. This is my number-one tip for easy removal and clean slicing later. I’ve tried just greasing the pan, and trust me, the parchment is worth the extra 30 seconds. Now, in my large bowl, I whisk together the melted (and slightly cooled!) butter with the brown and granulated sugars. I whisk for a good minute until it’s smooth and glossy. Then, I add the eggs, extra yolk, and vanilla. The mixture will look thick and creamy, like a luxurious caramel sauce. This is the base that holds everything together, and taking your time here ensures a perfectly blended dough.
Next comes the dry ingredients. I directly whisk the bread flour, baking soda, baking powder, and salt right into the wet mixture. I do this in two additions to avoid a flour cloud in my kitchen. I switch to a sturdy rubber spatula once it gets thick. The dough will be very thick and a bit shaggy—this is exactly what you want for a chewy bar. Overmixing is the enemy of tenderness, so I mix just until the last streaks of flour disappear. The smell of the raw dough at this point is already heavenly.
Now for the fun part: the mix-ins! I reserve about a half cup of the M&Ms and a handful of sprinkles for the top. Then, I gently fold in the remaining M&Ms, white chocolate chips, and sprinkles with my spatula. I’ve learned that if you stir too vigorously, the color from the M&Ms can start to bleed. A gentle folding motion preserves those beautiful, distinct pops of color. I then press this gloriously chunky dough evenly into my prepared pan. It takes a bit of patience, but I use the bottom of a measuring cup or my fingers to press it firmly into every corner.(See the next page below to continue…)