In a medium bowl, whisk the flour, ground ginger, ground cinnamon, kosher salt, baking soda, baking powder, ground cloves, and ground nutmeg.

In a separate bowl or the bowl of a stand mixer, whip the butter on high speed until light and fluffy. Add the dark brown sugar and molasses, followed by the buttermilk and egg, mixing on medium-high speed until well combined.

With a rubber spatula or a wooden spoon, fold the dry ingredients into the butter mixture until just combined. Do not overmix.

Cover the bowl with plastic wrap and transfer to the refrigerator to chill, at least 2 hours.

To bake, preheat the oven to 350 degrees F. Line 2 rimmed half-sheet trays with baking parchment.

Use a cookie scoop to portion the chilled dough onto the prepared trays in 1 ½-inch mounds, about 2–3 inches apart.

Bake for 13–15 minutes, or until the cakes spring back when touched.

Allow the cakes to cool on the tray for 5 minutes, then transfer to a wire rack to cool completely. Meanwhile, prepare the apple compote.

In a medium saucepan, combine the diced apples, water, granulated sugar, vanilla bean paste, ground cinnamon, and ground nutmeg.

Simmer over medium heat, stirring periodically, until the mixture thickens and the apples have broken down, about 20 minutes. If the pan seems dry, add an additional teaspoon of water as needed.

Remove from heat and stir in the lemon juice. Set the compote aside and allow it to cool completely before assembling the whoopie pies. Meanwhile, prepare the buttercream.

In a large mixing bowl or the bowl of a stand mixer, add the butter and whip on high speed until light and fluffy.

Gradually add the powdered sugar to the butter, alternating with the milk and mixing well after each addition. Continue mixing on medium-high speed until smooth and creamy.

Mix in the vanilla bean paste and salt. If necessary, add a teaspoon of milk to adjust the consistency.

Add the chopped toasted walnuts and mix on medium-high speed until well combined.

Transfer the buttercream to a piping bag fitted with a ⅝-inch round piping tip.

Divide the cakes into pairs, pairing halves that are similar in size and shape.

On the flat sides of half of the cakes, pipe a generous ring of walnut buttercream around the outside edge. Fill the center of each ring with a teaspoon of the apple compote.

Sandwich with the remaining cakes, pressing down gently to join the 2 halves.

Serve and enjoy.

Gingerbread whoopie pies are best enjoyed on the day they are made. Layer leftovers between sheets of baking parchment and store in an airtight container in the refrigerator for up to 5 days.