Melt butter in a large pot over medium heat. Add marshmallows and stir until melted.
4 tablespoons unsalted butter, 10 oz mini marshmallows
Stir in pumpkin puree, pumpkin pie spice, cinnamon, and vanilla extract until smooth.
¼ cup pumpkin puree, 1 teaspoon pumpkin pie spice, ¼ teaspoon cinnamon, ½ teaspoon vanilla extract
Remove from heat and stir in Rice Krispies until fully coated.
6 cups Rice Krispies cereal
Press the mixture evenly into the greased pan.
Melt white chocolate chips in a microwave safe bowl in 300second increments and drizzle over the treats.
¼ cup white chocolate chips
Let them cool for 30 minutes before cutting into squares.
Notes
A quarter cup of pumpkin puree is the ceiling for a 6 cup batch. It's enough to flavor every bite, and going heavier to chase more pumpkin flavor is what starts costing you the crunch. If you want a stronger pumpkin hit, add another half teaspoon of pumpkin pie spice rather than more puree.