In a medium bow sift or whisk together the flour and salt, set aside.
In the bowl of a stand mixer with the paddle attachment, or using a handheld mixer, cream the butter and sugar together on medium speed until light and fluffy, about 3-4 minutes. Add the vanilla and mix until combined.
Add the flour mixture to the butter mixture. Mix on low until the dough forms.
Pour in the chocolate chips and mix until just combined.
Place the dough into the middle of a sheet of wax paper (the sheet should be about 20 inches long). Roll the dough to form a long, even cylinder that is about 2 inches in diameter. Roll the wax paper around it and twist the sides closed. It will be about 18 inches long. Chill in the refrigerator at least 1 hours (best if overnight).
Preheat oven to 350 degrees F, and line a cookie sheet with parchment paper or a silicone baking mat.
Use a sharp knife to slice the log into 1/4 inch slices. You should get about 30 cookies. Place the cookie dough slices on the prepared cookie sheet, spacing them apart about 3/4 of an inch (they don't spread very much).
Bake for 5 minutes, then remove the cookies from the oven. Quickly place the M&M candies on top, nestling them lightly into the cookies. Return the pan to the oven and bake an additional 5-7 minutes, or until the edges just start to brown.
Let the cookies cool on the cookie sheet for 5 minutes, then transfer them to a wire rack to cool completely.