This sweet potato gratin has been a favorite in our home for many years. It makes a beautiful side dish for Thanksgiving, and the flavors blend beautifully with either Turkey or Ham. You can substitute Machengo, Romano, Gouda or Asagio cheeses as all of these work well in this gratin.
1 1/2 cups Heavy Cream (Full Fat Coconut Milk can be substituted)
2 Garlic Cloves, minced
1 Tablespoon chopped fresh Rosemary
1 Tablespoon chopped fresh Thyme
2 Tablespoons chopped Fresh Sage
Sea Salt and Freshly Ground Pepper, to taste
2 Pounds Sweet Potatoes (peeled and sliced into 1/8 thick slices)
1/2 Sweet Onion, thinly sliced or diced
3 Cups grated Gruyère cheese
1 Cup grated Parmesan cheese
Preheat oven to 375°F
Butter an 11-inch gratin dish or use a 9×13 oven safe dish.
In a large saucepan over medium heat, combine the cream, garlic, rosemary, thyme, sage, sea salt and pepper. Bring to a soft boil, then remove from the heat and set aside.
Place the sliced potatoes in a large shallow bowl and pour the cream mixture over the potatoes.
Gently stir the potato slices to coat with the cream mixture. (note: I use my hands for this step, a bit messy, but easier and faster to coat the potatoes)
Arrange one-third of the potato slices, slightly overlapping, on the bottom of the prepared dish. Sprinkle generously with salt and pepper, half of the onions and 1 cup of the Gruyère. Repeat, using another one-third of the potato slices, salt and pepper, the remaining onions, and another cup of the Gruyère.
Top with the remaining potatoes and sprinkle with salt and pepper again.
Press the mixture down gently with a spatula, (again, I just use the palms of my hands).
Pour any cream mixture over the potatoes and sprinkle evenly with the remaining Gruyère and Parmesan cheese.
Cover the dish with aluminum foil and bake for 45 minutes, then remove the foil and bake until the gratin is golden brown and bubbly, about 20 minutes more.
Let the gratin rest for 10 minutes before serving and garnish with sprigs of Sage leaves.