Melt butter in the microwave, or over low heat on the stovetop and set aside to cool.
1/2 cup unsalted butter
In a medium bowl, whisk together flour, baking soda and salt. Set aside.
1 1/4 cups all purpose flour, 1/2 teaspoon baking soda, 1/8 teaspoon salt
In a large bowl using a hand mixer or the paddle attachment on a stand mixer to beat the melted and cooled butter, light brown sugar and granulated sugar until combined.
1/2 cup light brown sugar, 1/4 cup granulated sugar
Add the vanilla and egg, beating on low speed until just combined.
1 teaspoon pure vanilla extract, 1 egg
Gradually add the flour mixture to the wet mixture and mix on low speed until combined.
Add in chopped candy and M&Ms, and stir until evenly combined.
Use a medium cookie scoop to scoop out even portions of dough and roll each in your hands. Place each ball on parchment paper on a baking sheet or platter, top with a sprinkle of salt (optional, but recommended), cover with plastic wrap and place in the fridge for 1-2 hours to chill.If you find that the dough is too soft to work with, place it in the fridge for 15-30 minutes first to let it firm up a bit.
Flaky sea salt
Preheat oven to 350°F and line two baking sheets with nonstick silicone mats or parchment paper.
Transfer dough to prepared baking sheets, at least 1-inch apart. I recommend doing no more than 6 cookies per baking sheet, just to give yourself plenty of room.
Bake one sheet at a time on the middle rack for 11 minutes, or until the edges have just started to turn golden brown
Remove from the oven and let cook on baking sheets for a few minutes, then transfer to wire racks to cool completely. Enjoy!
Video
Notes
Storage: Store in an airtight container for up to 5 days. I highly recommend adding a piece of bread to the container for the first two days to keep them soft!
Yield: Depending on the type and amount of candy you add, your dough may bulk up differently and this could cause variance in the number of cookies your dough yields.
Type of candy: Don't try to use fruity candies like Starbursts - stick to chocolate candies like KitKats, Mr. Goodbars, Milky Way, 3 Musketeers, Reeses, Hershey's, etc.