Step 1: Make cookies
Preheat oven to 350 degrees. Combine dry ingredients in a large bowl and set aside. In an electric mixer bowl, beat butter and sugars together until light and fluffy. Beat in eggs and vanilla until well blended. Slowly beat in milk and pumpkin puree. Add dry ingredients and beat just until blended. Using a tablespoon or small cookie scoop, drop dough onto parchment-lined baking sheets. Bake for 12 to 14 min., or until bottoms are lightly browned and tops are firm. Cool for about 5 min. on the baking sheet, then loosen the bottoms with a spatula and cool completely on a wire rack.
Step 2: Make filling
In an electric mixer bowl, beat together all filling ingredients until smooth. Spread filling on the bottom of a cookie, then press the bottom of another cookie on the filling to make a sandwich. Repeat with remaining cookies.