Preheat oven to 350 degrees Fahrenheit. Lightly spray a muffin tin with nonstick baking spray. In the bowl of an electric mixer, cream together butter, sugars, vanilla and peppermint extract and eggs until well combined. Add in flour, salt and baking soda and mix until combined. Roll into balls that will fit inside a muffin tin with a little extra space around the outside. Press each dough ball down with your thumb so it makes an imprint in the center. Bake for approximately 8 minutes. Remove from oven and immediately use a spoon to gently press down the center of each. Allow them to cool for a little while, then gently run a butter knife around the edges to release each one and carefully lift them out. Place them on a cooling rack to cool completely.
