Ingredients
- 3 lb (1.4 kg) mixed root vegetables, sliced 1/8 inch thick (Yukon gold, sweet potato, parsnip, rutabaga, carrot)
- 2 Tbsp unsalted butter
- 1 Tbsp olive oil
- 1 small shallot, minced
- 3 Tbsp all-purpose flour (or 2½ Tbsp cornstarch + 3 Tbsp water for gluten-free)
- 2 cups heavy cream
- 1 cup whole milk
- 2 tsp fresh thyme leaves (or 1 tsp dried)
- 1 pinch nutmeg
- 2 cloves garlic, minced
- 1 1/4 tsp kosher salt
- 1/2 tsp black pepper
- 2 cups (8 oz / 225 g) shredded Gruyère cheese, divided
- 3/4 cup panko breadcrumbs
- 1/2 cup finely grated Parmesan cheese
- 2 Tbsp olive oil (for topping)
- 2 Tbsp chopped sun-dried tomatoes (optional)
- 1 Tbsp chopped parsley (for topping)
Equipment
- mandoline slicer for even root slices
- 9×13-inch baking dish
- saucepan for cream sauce
- whisk
- foil for covering dish
- oven
- mixing bowl for crumb topping
Method
- Preheat oven to 375°F (190°C). Grease a 9×13-inch baking dish.
- In a saucepan, heat butter and olive oil over medium heat. Add shallot and sauté 3–4 minutes. Stir in flour and cook 1 minute.
- Whisk in cream and milk gradually. Add thyme, bay leaf, garlic, nutmeg, salt, and pepper. Simmer 3–5 minutes until lightly thickened. Remove bay leaf.
- Layer half the sliced roots in the dish, seasoning lightly. Pour half the sauce and sprinkle 1 cup Gruyère. Repeat with remaining roots, sauce, and 1 cup Gruyère.
- Cover tightly with foil and bake 45–50 minutes.
- In a bowl, mix panko, Parmesan, olive oil, sun-dried tomatoes (if using), and parsley. Uncover gratin, top evenly with crumb mix, and bake 20–25 minutes until golden and tender (center ~205°F/96°C).
- Rest 15 minutes before slicing. Garnish with parsley and serve warm.
Nutrition
Calories: 290kcalCarbohydrates: 27gProtein: 9gFat: 17gSaturated Fat: 10gPolyunsaturated Fat: 1gMonounsaturated Fat: 5gCholesterol: 50mgSodium: 420mgPotassium: 680mgFiber: 4gSugar: 7gVitamin A: 9500IUVitamin C: 14mgCalcium: 190mgIron: 2mg
Notes
Vegetarian: Use cheeses made with vegetarian rennet.
Gluten-free: Replace flour with 2½ Tbsp cornstarch mixed with 3 Tbsp water.
Lighter version: Swap 1 cup cream for milk and add extra thyme.
Equipment: Mandoline, 9×13-inch baking dish, foil.
Alternate Methods: Mini gratins (ramekins): Bake at 375°F (190°C) 30–35 min covered, then 10–12 min uncovered to brown.
Convection oven: 350°F (175°C); start checking 10 minutes earlier for doneness.
Gluten-free: Replace flour with 2½ Tbsp cornstarch mixed with 3 Tbsp water.
Lighter version: Swap 1 cup cream for milk and add extra thyme.
Equipment: Mandoline, 9×13-inch baking dish, foil.
Alternate Methods: Mini gratins (ramekins): Bake at 375°F (190°C) 30–35 min covered, then 10–12 min uncovered to brown.
Convection oven: 350°F (175°C); start checking 10 minutes earlier for doneness.
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