01 -
In a large mixing bowl, whisk together all-purpose flour, salt, baking soda, cornstarch, and baking powder. Set aside.
02 -
In a separate bowl, combine cold cubed butter, brown sugar, and granulated sugar. Mix with a stand mixer on low speed just until most of the butter is incorporated but still slightly cold. Avoid overmixing.
03 -
Add vanilla extract, egg yolks, and whole egg to the butter mixture. Mix until fully integrated.
04 -
Gradually mix half of the dry ingredients into the wet mixture until just combined. Add the remaining dry mixture and blend until a cohesive dough forms.
05 -
Lightly toss M&Ms in a small amount of flour to prevent sinking.
06 -
Gently fold the prepared M&Ms into the cookie dough by hand, distributing evenly.
07 -
With a cookie scoop or scale, portion dough into approximately 6 tablespoons (about 90 grams) per cookie. Place cookies spaced well apart on a parchment-lined baking sheet.
08 -
Press additional M&Ms lightly onto the tops of each portioned dough ball for a festive appearance.
09 -
Refrigerate the formed dough for at least 3 hours or overnight to ensure thick, bakery-style cookies and to prevent overspreading.
10 -
Preheat the oven to 175°C (350°F). Bake cookies for 17 minutes, or until edges are lightly golden while centers remain soft.
11 -
Allow cookies to cool on the baking tray for several minutes before transferring to a wire rack. Serve once fully cooled.