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 fully incorporated and smooth.
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 combined. Fold in rolled oats using a spatula.
06 - Drop tablespoon-sized dough portions onto prepared baking sheets, spacing 2 inches apart to allow spreading.
07 - Bake for 10-12 minutes until edges are lightly golden and centers are set. Cool on sheets for 5 minutes before transferring to wire rack.
08 - Beat butter until creamy. Gradually incorporate powdered sugar, cream, vanilla, and salt. Continue beating until light, fluffy, and spreadable.
09 - Pair cookies of similar size. Spread approximately 1 tablespoon filling onto flat side of one cookie and press another cookie on top to create sandwich.