Preheat your oven to 350°F (175°C). In a large mixing bowl, beat together the butter and brown sugar until light and fluffy, about 3-4 minutes. Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.

In another bowl, whisk together the rolled oats, flour, baking soda, and spices. Gradually add this mixture to the wet ingredients, stirring until combined to form a sticky dough.

Line your baking sheets with parchment paper. Using a cookie scoop, drop tablespoon-sized balls of dough onto the sheets, spacing them about 2 inches apart. Bake for 10-12 minutes until the edges are golden brown.

In a medium bowl, mix together the pumpkin puree, powdered sugar, butter, vanilla extract, and cinnamon. Beat until smooth and creamy, about 2-3 minutes.

Spread a generous layer of the pumpkin filling on the flat side of one cookie, then place another cookie on top, pressing lightly. Repeat until all cookies are filled.