Position a rack in the center of the oven and preheat the oven to 375 degrees F. Line a large baking sheet with parchment paper or nonstick aluminum foil.
Melt the base. In a medium pot on medium heat, add the brown sugar, butter and pumpkin pie spice. Cook, stirring, until the butter melts and the mixture is less gritty.
Finish the batter. In a large bowl, add the oats, flour, almond extract and egg and toss. Slowly add the butter mixture from the pot while constantly stirring the oat mixture.
Bake and rest. Use a teaspoon to drop the batter on the prepared baking sheet about 3 inches apart to allow spreading. This will take patience and several batches. Also, to avoid a big glob, try to gently press the oats so they aren't in a mound.
Bake on the center rack until the edges are caramelized and the centers stop rapidly bubbling, 5 to 6 minutes. Remove and leave on the baking sheet for 5 minutes, then transfer the entire sheet of parchment onto a wire rack. After a few more minutes, transfer the cookies from the parchment to rest directly on the wire rack. Continue until all the batter is cooked and the cookies are fully cool and rigid, 15 to 20 minutes.
Fill and serve. Pick 2 cookies with approximately the same size and shape and spread about 1/2 teaspoon of raspberry jam on the bottom/flat side of one cookie, then sandwich the matching cookie's bottom/flat side to the other; repeat until done. Store in an airtight container in a cool place, even the fridge, for up to 1 week. Happy holidays and happy cookie making!