Melt 3 tablespoons of unsalted butter in a microwave safe bowl. Add 2 tablespoons of sugar and 8 ounces of gluten free graham cracker crumbs and mix well.
Spray a 9x13 pan with nonstick cooking spray, then press the graham cracker mixture into the bottom and about 1/2 way up the sides.
Bake for 8-10 minutes at 350°. Let cool slightly while you prepare the cheesecake.
For the Cheesecake
In the bowl of an electric mixer fitted with a paddle attachment, mix softened cream cheese and sugar until light and fluffy, about 2 minutes.
Add eggs and vanilla extract and mix until well combined, scraping down the sides and bottom of the bowl with a rubber spatula.
Add in spices and pumpkin purée and mix until just combined. Using a rubber spatula, scrape the sides and bottom of the mixing bowl to ensure cheesecake mixture is fully combined with pumpkin purée.
Bake cheesecake for 25-30 minutes at 350°, or until a knife inserted into the center comes out clean. Cheesecake should still be a bit wobbly in the center.
Switch oven from bake to broil (low temp or about 425).
Sprinkle mini marshmallows on top of cheesecake and place back in the oven under broiler for about 2-3 minutes. Being careful not to burn marshmallows.
Let cheesecake cool to room temperature, then chill in refrigerator for about 2-3 hours before serving.
Notes
Be sure to spray a sharp knife with nonstick cooking spray before you cut the cheesecake bars! Otherwise the marshmallows will stick and pull off the top of the cheesecake. Cheesecake can be stored covered in the refrigerator for about 2-3 days.