01 -
Preheat oven to 350°F (175°C) and line two large baking sheets with parchment paper.
02 -
In a large bowl, beat the softened butter, brown sugar, and granulated sugar together using an electric mixer until pale and creamy for 2-3 minutes.
03 -
Add the vanilla extract, light corn syrup, and egg. Mix until just combined without overbeating.
04 -
In a separate bowl, whisk together flour, baking soda, and salt. Gradually add to the wet mixture, mixing on low speed until a soft but manageable dough forms. Add extra flour by the tablespoon if the dough is too sticky.
05 -
Using a spatula or your hands, gently fold in half of the chocolate chips and half of the M&M's until evenly distributed throughout the dough.
06 -
Scoop cookie dough into 1-tablespoon sized balls for 18-20 medium cookies or 2-tablespoon sized balls for 12 jumbo cookies. Place dough balls at least 3 inches apart on prepared baking sheets.
07 -
Press remaining chocolate chips and M&M's gently into the tops of each dough ball for a festive appearance.
08 -
Bake cookies in preheated oven for 11-12 minutes. Remove when edges are golden but the centers look pale and soft; do not overbake.
09 -
Gently tap baking sheets on the counter to release trapped air for even texture. Allow cookies to cool on the baking sheets for about 30 minutes to finish setting before transferring.