Cream your butter and sugar in your mixing bowl.
Add the egg and the remaining dry ingredients. Add your chocolate chips and m&m's last and allow to combine.
The dough should begin to stick to the paddle as it's being rotated around in the mixing bowl. Roll out the dough. My preferred way to do this is by putting the dough on parchment paper, and then placing another piece of parchment paper on top of the dough. This way you can rotate the dough around and roll out evenly. Cut out your cookies with a heart-shaped cookie cutter. After you have your heart shaped chocolate chip cookies cut out, move them to a parchment paper covered baking sheet and freeze for 10-12 minutes. This will help minimize the spread. These cookies will still spread quite a bit, as you can see from the before/after photos, but this step does help limit the expansion.
Pop them in the oven for 10-11 minutes, checking on them periodically. Baking time will vary depending on your oven and the humidity in your home.
Remove from the oven and, this is important, leave them on the baking sheet for about 5 minutes. They will continue to bake on the pan and you don't want to remove them too quickly. If the shapes have completely 'blubbed' you can use a knife or spoon to push in the dough a bit while it's still hot.
Top with a pinch of sea salt for extra flavor. Transfer to a cooling rack and allow to cool before decorating or sharing.