Cream 1 cup cold-soft butter, 1 cup brown sugar, 1/2 cup sugar. Add 1 egg, 1/2 cup sourdough discard, 2 tsp vanilla. Mix in: 1.5 cups flour, 1 tsp baking soda, 1/2 tsp salt, 1/4 tsp each nutmeg, cloves, cinnamon, and 3 cups quick oats. Scoop onto parchment-lined sheet, bake at 375°F for 10–12 mins. Cool, then sandwich with cream filling.

Cream Filling:

Beat 1/2 cup butter, 2 cups powdered sugar, 1–2 TBSP cream, 1 tsp vanilla until fluffy.