Chefs Melody Bishop and Dennis Kelley from Lark on the Park cook up some sweet potatoes with caramelized onions and gruyere.
Sweet Potato Gratin
1 tablespoon unsalted butter plus more for dish
4 pounds sweet potatoes, about 6 potatoes
1 pound yellow onion, sliced
1/4 cup extra virgin olive oil
2 tablespoons butter
2 teaspoons fresh thyme leaves, divided plus 4 sprigs
3 cups heavy cream
1 each cinnamon stick
1 each allspice
1 each fresh bay leaf
2 sprigs fresh thyme
pinch freshly grated nutmeg
2 ea black peppercorns
2 sprigs fresh sage, leaves from 1 sprig thinly sliced
2 teaspoons Freshly ground black pepper
2 tablespoons kosher salt
1 cup coarsely grated Gruyère cheese
DO AHEAD: Caramelized Onions and infused cream can be made 4 days ahead and kept refrigerated in tightly sealed container.
Lightly butter a 3-quart baking dish. Preheat oven to 400 degrees.
Add cream, herbs and spices to a saucepan and bring to a simmer. Take off heat and let stand 1 hour to infuse. Strain herbs and spices and discard. Season mixture with salt and pepper. Set aside or refrigerate for up to 4 days.
In a large sauté pan heat olive oil over high heat. Once pan is hot and lightly smoking add sliced onions, 1 teaspoon salt, 1/4 teaspoon freshly cracked pepper and 2 sprigs fresh thyme. Toss to combine. Turn heat to low and slowly cook, stirring occasionally for about 15 minutes until onions are golden brown. Remove from heat and set aside or refrigerate in air tight container for up to 4 days.
Thinly slice sweet potatoes on a mandoline.
TO ASSEMBLE: Pour 1/4 cup cream in bottom of the buttered baking dish.
Starting in the top corner of the dish, layer sweet potato slices overlapping in straight rows, overlapping each row about 1/4 inch. Sprinkle with 1/2 teaspoon salt, pinch black pepper, 1/2 teaspoon thyme leaves, 1/2 teaspoon sliced sage and 1/4 cup infused cream. Repeat with a second layer. Top with 1/2 cup grated gruyere, 1 cup caramelized onions and spread evenly.
Starting in the top corner of the dish repeat with another layer of potatoes. Sprinkle with 1/2 teaspoon salt, pinch black pepper, 1/2 teaspoon thyme leaves, 1/2 teaspoon sliced sage and 1/4 cup infused cream. Repeat with one more layer.
Drizzle top with 1/4 cup cream, 1/2 cup grated gruyere, 1/2 teaspoon thyme leaves and 1/4 teaspoon slivered arbol chili.
Cover with foil and bake at 400 degrees for 45 minutes until potatoes are tender when pierced with a fork or tip of a sharp knife.
Remove foil and bake 5 more minutes until lightly browned.
Remove from oven and let rest 10 minutes. Cut into squares and serve.
DO AHEAD: Gratin can be assembled and baked 1 to 2 days ahead. Cool, cover and refrigerate. Preheat oven to 325 degrees about 30 minutes or until warm through and a little bubbly.