Preheat oven to 350 degrees
Using the medium bowl, combine the flour, baking soda, cinnamon, and salt. Mix it with a whisk.
In the stand mixer bowl (or a large bowl with hand mixer), combine the butter, brown sugar, and granulated sugar. Beat with a paddle attachment if you have one until it is creamy and smooth. Beat it for about 2 minutes scraping sides of bowl with spatula as needed.
Add the egg, egg yolk and vanilla and mix until smooth.
Carefully add the dry ingredients to the creamy mixture. On low, mix until combined and then add the oats.
Prepare the baking sheets with parchment paper.
Place about a tablespoon sized spoonful of dough on the baking sheet and use the butter knife to remove it from the spoon. Fill the baking sheet with cookies. NOTE: If you are using sprinkles, smash the cookies and sprinkle the cookies before you bake them. If you are using M & M's do not smash cookies and wait till they come out of oven to add M & M's
Bake the cookies for 10-12 minutes until the edges of the cookies are golden brown.
Remove cookies from oven and immediately place several M & M's on each cookie (if they are not sprinkled) ... press down a little so they stick. Let cool on sheet for 5 minutes than remove to cooling rack.