01 -
Preheat oven to 400°F. Spray a 9x13-inch baking dish with cooking spray.
02 -
Layer sweet potato slices in the prepared dish, slightly overlapping each slice.
03 -
In a medium saucepan, melt butter over medium heat. Add shallot and garlic, cooking 2-3 minutes until softened.
04 -
Reduce heat to low. Add heavy cream, Parmesan, Gruyere, salt, and pepper. Stir until cheese is fully melted and mixture is smooth. Remove from heat.
05 -
Pour cheese sauce evenly over sweet potatoes. Cover tightly with aluminum foil and bake for 30 minutes.
06 -
Remove foil and continue baking for 20-30 minutes, or until sweet potatoes are fork-tender and top is lightly golden.
07 -
Remove from oven and let rest for 5 minutes. Garnish with chopped chives before serving.