In a large bowl, with a handheld or stand mixer, cream together butter, peanut butter, egg, vanilla and sugars until smooth.
Slowly mix in the dry ingredients to the peanut butter mixture. Scrape down the bowl as necessary. Mix until totally blended together. Add M&M's, chocolate chips or chunks or nothing at all. It is up to you.
Wrap dough in parchment paper and place it in your fridge for at least an hour.
Preheat your oven to 325 degrees. Prepare a rimmed baking sheet lightly coated in cooking spray.
Remove dough from fridge and make rounds or discs of 1/2 to 3/4 of an inch high and 1 1/2 to 2 inches in diameter.
Spread a thin layer of granulated sugar on a plate and adjust each dough disc until evenly coated in sugar. This step is not mandatory. Feel free to skip it if you want. I never do. My husband always does.
Bake for about 16-20 minutes or until cookies just start to crack and brown around the edges. They will not look cooked in the middle. You do not want these cookies to become hard so do not over bake them.
Allow cookies to cool on the baking sheet for at least 7-10 minutes before transferring them on to a rack. Serve and enjoy every bite!
You can also press a chocolate Hershey's kiss into each cookie as soon as they come out of the oven and quickly stick the baking sheet in the freezer or fridge. I usually lay a towel down so I don't melt the shelf in my fridge or freezer. If you don't do this the cookies will totally melt the chocolate. Leave the cookies in your fridge for about 30 minutes or freezer for about 20 minutes. Just make sure the cookies are cool when you remove them from the fridge or freezer! These are delicious too and are definitely worth a try!
Store in an airtight container at room temperature for up to 5 days, or in the freezer for up to 3 months. You also have the option of storing the unbaked cookie dough in the freezer for up to 3 months as well.