Preheat your oven to 375 degrees.
Peel those tender sweet potatoes, and with the trusty hand blender, blend them up until silky smooth.
In goes the sugar, eggs, butter, evaporated milk, ground cinnamon or pumpkin pie spice, and vanilla. Blend until everything is beautifully incorporated.
Spray your baking dish with non-stick spray and transfer that heavenly mixture into it.
Bake it in the preheated oven for about 13-15 minutes until it gets that gorgeous golden color.
Now, for the pièce de résistance – the marshmallow topping! Arrange those mini marshmallows in a single layer on top of the casserole.
Crank up the heat to 450 degrees and let the marshmallows work their magic for 8-10 minutes until they're beautifully toasted.