Preheat the oven to 350 F. In a medium bowl, whisk together flour, salt, and baking soda. In a large bowl, combine butter and sugar until fluffy. Add in egg and vanilla extract, and mix until smooth.
Add in the flour mixture, mix until it is fully combined. Fold in the M&Ms. Roll the cookie dough into balls, and flatten each slightly. Place one Oreo cookie onto each piece of dough, and cover it fully with the dough, rolling it into a ball.
Place the cookies onto a large ungreased baking sheet. Bake for 10-12 minutes.
