Instructions

• Heat oven to 350° and butter a 2-quart gratin dish. Wash the leeks to remove any grit and slice thinly crosswise.
• Using a mandoline or sharp knife, slice the potatoes into 1/8″ thick rounds. Toss with 3/4 tsp salt and 1/4 tsp pepper. Layer the rounds in the gratin dish. (Em-i-lis note: Don’t pour the potatoes in as by this point they will released a decent amount of water and you don’t want that soupifying your grating).
• Melt the 2T butter in a large skillet over medium heat. Add leeks, remaining salt and pepper, and thyme. Cook, stirring, until leeks are tender and golden, 5-7 mins. Discard thyme and scatter the leeks over the potatoes.
• Add cream, garlic and bay leaf to the skillet, scraping up browned bits of leeks from the bottom of the pan. Simmer gently for 5 minutes. Stir in nutmeg.
• Pour the cream mixture over the leeks and potatoes. Top with the shredded Gruyère. Cover with foil and put in the oven. Bake for 40 minutes, uncover and bake until the cheese is bubbling and golden, 15-20 minutes longer. Let cool slightly before serving.