Preheat the oven to 350 degrees F. Arrange 14 of the biscuits into a "+" shape in a 18-by-13-inch rimmed baking sheet. You should have 4 equal quadrants. (Reserve the remaining biscuits for another use.) Refrigerate until ready to use.
For the cranberry sauce: Mix together the cranberries, sugar, orange juice and cornstarch in a medium bowl until well combined and set aside.
For the sweet potato casserole: Place the sweet potatoes in a medium microwave-safe bowl and cover with plastic wrap. Microwave until soft and easy to mash with a fork, about 12 minutes. Add in the milk, butter, sugar, vanilla, 1 1/2 teaspoons salt and a few grinds of pepper and mash with a fork or a potato masher until smooth with just a few chunks and set aside.
For the green bean casserole: Heat the oil in a medium non-stick skillet over medium-high heat. Add the mushrooms and onion and cook, stirring occasionally, until the mushrooms are soft and have released most of their liquid, 5 to 6 minutes. Sprinkle the flour over the vegetables then stir in the heavy cream, 1 1/2 teaspoons salt and a few grinds of pepper. Cook, stirring frequently, until the sauce has thickened, 2 to 3 minutes. Fold in the green beans until well coated and set aside.
For the scalloped potatoes: Slice the potatoes 1/8-inch-thick and transfer to a medium microwave-safe bowl along with the heavy cream, Parmesan, garlic, thyme, 1 1/2 teaspoons salt and a few grinds of pepper. Toss to coat and microwave until softened, about 7 minutes. Set aside.
Assemble the sheet pan: Pour the cranberry mixture into one quadrant of the baking sheet and sprinkle with the turbinado sugar. Spread the sweet potatoes into a second quadrant and sprinkle with the marshmallows. Pour the green bean mixture into a third quadrant and sprinkle with the crispy onions. Spread the scallop potato mixture into the final quadrant and sprinkle with the Gruyere.
Bake until the biscuits are cooked through and golden brown, the cranberries are bubbling and bursting, the marshmallows have turned golden brown and the scalloped potatoes are cooked through, 30 to 35 minutes. Let cool 5 minutes before serving.
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