Creamy Potato and Leek Bake with Gruyère

1. Prep and Assemble

Preheat the oven to 350°F (175°C). Grease a 2-quart gratin dish with butter. Clean the sliced leeks thoroughly to remove any dirt. Set aside. Slice potatoes into 1/8-inch thick rounds using a mandoline or a sharp knife. In a bowl, toss them with 3/4 tsp salt and 1/4 tsp pepper. Arrange the seasoned potato slices into the prepared dish in an even layer.

2. Cook Leeks

In a skillet, melt 2 tbsp butter over medium heat. Add sliced leeks, the remaining 1/4 tsp salt and 1/4 tsp pepper, and thyme sprigs. Sauté for 5-7 minutes until leeks are soft and golden. Remove and discard the thyme, then evenly distribute the leeks over the potatoes in the dish.

3. Cream Mixture

To the same skillet, add heavy cream, chopped garlic, and bay leaf. Scrape up any leek remnants from the pan and simmer for 5 minutes. Remove and discard the bay leaf. Stir in the ground nutmeg.

4. Bake

Gently pour the cream mixture over the layered potatoes and leeks. Sprinkle the grated Gruyère on top. Cover the dish with aluminum foil and bake for 40 minutes. Remove the foil and continue to bake for another 15-20 minutes, until the cheese is golden and bubbly. Allow the gratin to cool slightly before serving.