1 cup marshmallow sauce, store-bought (such as: TBD…)
3 cups butter pecan ice cream
1 cup whole milk
12-16 mini marshmallows
Preheat the oven to 375 degrees F.
To roast the sweet potatoes: In a medium bowl, add sweet potatoes, 3 tablespoons melted butter, brown sugar, 1/2 teaspoon pumpkin pie spice and 1/2 teaspoon of salt.
Toss to combine until potatoes are evenly coated with butter and sugar. Arrange in one layer onto a foil-lined baking sheet.
To make the crumble topping: In a medium bowl, combine the oats, 1 tablespoon of sugar, flour, pecans, and remaining salt.
Using your fingertips, cut the cubed butter into the oat mixture until the butter is fully incorporated and the mixture is clumpy.
Pour into a greased and floured medium cast iron skillet, then gently spread into an even layer, keeping the clumps intact.
Bake the sweet potatoes and crumble for 20 minutes. Set aside to cool.
To make the spiced sugar: In a small, shallow dish, combine the remaining 1/2 cup of sugar, remaining pumpkin pie spice and a pinch of salt. Set aside.
Marshmallow sauce: Using a funnel, transfer the marshmallow sauce from its store-packaged container into a squeeze bottle.
Cut the tip to yield a thick drizzle. Holding the serving glass for your milkshake in one hand and the squeeze bottle in the other, place the tip of the bottle inside the glass. Starting from the bottom, simultaneously rotate the glass while squeezing the marshmallow sauce to adhere to the sides, creating an upward spiral pattern. Repeat with the second glass. Place in the refrigerator to set.
To make the milkshake: In a blender, add the butter pecan ice cream, milk, and cooled sweet potatoes. Blend until smooth.
Dip the rim of the chilled, prepared glasses into a shallow bowl of water. Then dip into the spiced sugar. Pour the milkshake into each glass, leaving an inch of room at the top. Top the shake with a spoonful of crumble topping. Dot with 6-8 mini marshmallows. With a butane torch, brown the marshmallows.