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 together until light and fluffy, approximately 2 minutes.
03 - Add eggs and vanilla extract to the butter mixture. Beat until thoroughly combined.
04 - In a separate bowl, whisk together flour, baking soda, baking powder, salt, and cinnamon until well blended.
05 - Gradually add dry ingredients to wet mixture, mixing just until incorporated. Fold in rolled oats using a spatula.
06 - Scoop tablespoon-sized portions of dough onto prepared baking sheets, leaving approximately 2 inches of space between each portion.
07 - Bake for 10 to 12 minutes until cookies are just set and lightly golden around edges.
08 - Let cookies rest on baking sheets for 5 minutes, then transfer to wire rack to cool completely.
09 - Beat softened butter in a medium bowl until creamy. Gradually incorporate powdered sugar, cream, vanilla, and salt. Continue beating until light, fluffy, and spreadable.
10 - Pair cookies of similar size. Spread or pipe approximately 1 tablespoon of cream filling onto flat side of one cookie, then press another cookie on top to form sandwich.