Preheat oven to 350 degrees F.

In a medium-sized bowl, beat cake mix, pumpkin puree, pumpkin pie spice and vegetable oil until smooth.

Using a medium cookie scoop, drop mounds of dough onto parchment lined baking sheets.

Bake for about 12-15 minutes, or until tops spring back lightly when touched. Remove from the oven and press cookies lightly with the back of a metal spatula to flatten slightly.

Meanwhile, cut marshmallows in half and set aside. You'll only need half as many marshmallows as you have cookies.

Cool on baking sheets for 2-3 minutes. Transfer half of the cookies to a wire rack, and flip the other half over on the baking sheet so the bottoms are facing up.

Place a large marshmallow on each of the overturned cookies. Slide the sheet back into the oven for 2-3 minutes, just until marshmallows start to puff up and about double in size.

Remove from the oven and cool for 2-3 minutes. Place the cooled cookies from the wire rack on top of the marshmallow to form a sandwich, pressing lightly and twisting gently to adhere.

Cool sandwiches completely on the wire racks. Watch them for a minute or so to make sure the tops don't slip off.

Store in an air-tight container for up to 5 days.