Potato Leek and Fennel Gratin
Elevate your side dish game with this luxurious Potato Leek and Fennel Gratin—a creamy, cheesy casserole that’s sure to impress. Thinly sliced russet potatoes are layered with sweet, caramelized leeks and fennel, then smothered in a velvety blend of heavy cream, milk, garlic, and thyme. A generous topping of Gruyere and Parmesan cheeses creates a golden, bubbly crust that’s pure comfort food. Perfect for holiday gatherings or elegant dinners, this gratin pairs beautifully with roasted meats or a fresh green salad. Ready in just over an hour, it’s the ultimate make-ahead dish that’s both hearty and refined. Experience the irresistible blend of flavors and textures in this crowd-pleasing potato gratin recipe!
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Recipe Information
Ingredients
- 4 large russet potatoes
- 2 medium leeks
- 1 large fennel bulb
- 3 tablespoons unsalted butter
- 2 cups heavy cream
- 1 cup whole milk
- 2 large garlic cloves
- 1 teaspoon thyme
- 2 cups grated Gruyere cheese
- 1 cup Parmesan cheese, grated
- 1 teaspoon kosher salt
- 0.5 teaspoon black pepper
- 1 tablespoon olive oil
Instructions
Preheat your oven to 375°F (190°C) and grease a 9x13-inch baking dish with butter or olive oil.
Peel the russet potatoes and slice them thinly into rounds, approximately 1/8-inch thick. Set the sliced potatoes aside in a bowl of cold water to prevent browning.
Trim the dark green portions of the leeks, keeping only the white and light green parts. Slice the leeks lengthwise, then rinse thoroughly to remove any dirt. Thinly slice the leeks crosswise.
Cut off the stalks and fronds of the fennel bulb, reserving a few fronds for garnish if desired. Slice the fennel bulb thinly.
In a large skillet, heat 1 tablespoon of olive oil and 1 tablespoon of butter over medium heat. Add the sliced leeks and fennel, and cook until they are softened and lightly golden, about 5-7 minutes. Set aside.
In a small saucepan, heat the heavy cream, milk, minced garlic, and thyme over medium-low heat until warm but not boiling. Stir occasionally. Season with kosher salt and black pepper.
Drain the potatoes and pat them dry with a clean kitchen towel.
Layer half of the sliced potatoes evenly at the bottom of the prepared baking dish. Season lightly with salt and pepper.
Spread half of the cooked leeks and fennel mixture on top of the potato layer. Sprinkle 1 cup of grated Gruyere cheese over the top.
Repeat with the remaining potatoes, leeks, and fennel. Pour the warm cream mixture evenly over the layered ingredients in the baking dish.
Sprinkle the top with the remaining Gruyere cheese and the Parmesan cheese.
Dot the top with the remaining 2 tablespoons of butter, broken into small pieces.
Cover the baking dish loosely with aluminum foil and bake in the preheated oven for 40 minutes.
Remove the foil and continue to bake for an additional 20 minutes, or until the top is golden brown and the potatoes are tender when pierced with a knife.
Allow the gratin to rest for 5-10 minutes before serving. Garnish with fennel fronds, if desired.
Nutrition Facts
Calories |
4834 | ||
|---|---|---|---|
% Daily Value* |
|||
| Total Fat | 315.6 g | 405% | |
| Saturated Fat | 182.5 g | 912% | |
| Polyunsaturated Fat | 2.1 g | ||
| Cholesterol | 882 mg | 294% | |
| Sodium | 4182 mg | 182% | |
| Total Carbohydrate | 332.5 g | 121% | |
| Dietary Fiber | 35.3 g | 126% | |
| Total Sugars | 46.8 g | ||
| Protein | 149.6 g | 299% | |
| Vitamin D | 3.0 mcg | 15% | |
| Calcium | 3968 mg | 305% | |
| Iron | 22.9 mg | 127% | |
| Potassium | 9069 mg | 193% | |
*The % Daily Value tells you how much a nutrient in a serving of food contributes to a daily diet. 2,000 calories a day is used for general nutrition advice.
