Prepare the graham cracker crumble according to the instructions and set aside.
Lightly spray a 9×13-inch pan with nonstick spray and set aside.
Place the pumpkin puree in a nut milk bag and gently squeeze out as much excess moisture as possible. If you don’t have a nut milk bag, place the pumpkin between several layers of paper towels and gently press to remove the excess moisture.
In a large pot over low heat, melt the butter, then stir in the salt.
Stir in the pumpkin pie spice and drained pumpkin puree and cook for about 30 seconds.
Add 12 ounces of the mini marshmallows and stir until completely melted and smooth.
Fold in the Rice Krispies cereal, the remaining 2 ounces of marshmallows, and the graham cracker crumble until evenly coated.
Transfer the mixture to the prepared pan and gently press into an even layer. Avoid packing the treats too firmly.
Let cool for 1 hour before cutting into 16 squares.