1. Preheat the oven to 350 degrees F. With an electric mixer, beat the butter and sugars in a large bowl until well combined, about 3-5 minutes. Add the egg and vanilla mix until light and fluffy, about 2 minutes.
2. In a separate bowl, whisk together the flour, baking soda, salt, and cinnamon. Add to butter and mix on low speed just until combined. Add the oats and stir until just combined.
3. Use a medium (1.5 tbsp) cookie scoop to place dough on a cookie sheet lined with parchment paper. Bake at 350 for 10 minutes until edges start to turn golden brown. Cool on a wire rack.

To make Buttercream Frosting

1. Place the butter, sugar, whipping cream and vanilla in a large mixing bowl. Beat on medium speed until smooth and creamy, about 2-3 minutes.
2. When the cookies are cool, sandwich frosting between two cookies. Enjoy!! :)