Reduce the Cider: In a medium saucepan, simmer 2 1/2 - 3 cups apple cider over medium heat until reduced to 3/4 cup, 20-30 minutes. Cool completely.

Preheat oven to 350°F (175°C). Line baking sheets with parchment paper.

In a medium bowl, whisk together flour, baking powder, baking soda, salt, cinnamon, nutmeg, and cloves.

In a large bowl, cream the softened butter and brown sugar until light and fluffy, about 3 minutes. Beat in the egg and vanilla extract until smooth.

With mixer on low, add the dry ingredients in three parts, alternating with the cooled reduced cider in two parts, beginning and ending with dry ingredients. Mix until just combined.

Scoop dough (about 1.5 tbsp each) onto baking sheets, 2 inches apart. Flatten slightly. Bake for 12-14 minutes until edges are set. Cool on sheet for 5 minutes, then transfer to a wire rack to cool completely.

Make Buttercream: Beat softened butter until creamy. Gradually add sifted powdered sugar, then vanilla and salt. Add cream until light and fluffy.

Assemble: Spread or pipe buttercream onto the flat side of half the cookies. Top with remaining cookies to form sandwiches.