01 - Preheat oven to 350°F. Line two baking sheets with parchment paper.
02 - In a large bowl, beat softened butter, brown sugar, and granulated sugar until light and fluffy, approximately 2 minutes.
03 - Add eggs and vanilla extract. Beat until thoroughly combined.
04 - In a separate bowl, whisk together flour, baking soda, baking powder, salt, and cinnamon.
05 - Gradually add dry ingredients to wet mixture, mixing just until incorporated. Fold in rolled oats using a spatula.
06 - Scoop tablespoon-sized portions onto prepared baking sheets, spacing 2 inches apart.
07 - Bake for 10 to 12 minutes until edges are lightly golden and centers are set.
08 - Let cookies rest on baking sheets for 5 minutes, then transfer to wire rack to cool completely.
09 - Beat butter until creamy. Gradually incorporate powdered sugar, cream, vanilla, and salt. Beat until light and fluffy.
10 - Pair cookies of similar size. Spread 1 tablespoon cream filling on flat side of one cookie and press another cookie on top to form sandwich.