Caramelized onions and sharp cheddar put a distinctive American spin on a traditional gratin.
Preparation time: 1 hour 15 minutes
1 organic onion, chopped
2 tablespoons expeller pressed canola oil
1 1/4 teaspoon salt, divided, more to taste
2 cups organic whole milk
2 sprig fresh organic rosemary
4 cloves organic garlic, minced
1 pound organic white potatoes, peeled and sliced into 1/8 inch thick rounds
1 pound organic sweet potatoes, peeled and sliced into 1/8 inch thick rounds
1 pound organic rutabaga, peeled and sliced into 1/8 inch thick rounds
Freshly grated black pepper to taste
Butter for greasing baking dish
1 1/2 cups grated sharp cheddar cheese
1. Preheat oven to 400°F. Heat oil in a 10-inch sauté pan or large frying pan over medium heat until shimmering. Add onions and stir to coat with oil. Sprinkle with 1/4 teaspoon of salt, reduce heat to medium low, and cook, stirring often, until onions are golden brown, about 25 minutes. Once caramelized, set aside.
2. Meanwhile, put milk, two cups of water, rosemary, garlic and one teaspoon of salt in a large pot and bring to a simmer over medium heat. Add white potatoes and cook until just tender when pierced with a fork, 5 to 10 minutes. Remove from milk and set aside in their own bowl. Repeat with the sweet potatoes and then the rutabaga, putting each vegetable in their own bowl. Note that cooking time on each vegetable will vary, with the rutabaga probably taking the longest. Reserve poaching milk.
3. Grease a 9-by-14 inch baking pan with butter. Layer the potatoes, sprinkle with salt and little black pepper and ½ cup of cheddar. Next layer the sweet potatoes, sprinkle with salt and a little black pepper and ½ cup of cheddar. Finish with the rutabaga, sprinkle with salt and a little black pepper, the caramelized onions, and remaining cheese. Ladle one cup of poaching milk onto the gratin, cover with aluminum foil, and bake for about 20 minutes. Remove foil and cook until lightly browned. Cool for 10 minutes before serving.