Name: Creamy Mushroom Lasagna
Ingredients: 1 lb. dried lasagna; 3½ tsp. Diamond Crystal or 2 tsp. Morton kosher salt, divided, plus more; 16 Tbsp. (2 sticks) unsalted butter, divided; 2 lb. crimini mushrooms, trimmed, thinly sliced; 1½ tsp. freshly ground pepper, divided, plus more; 3 shallots, finely chopped; 8 garlic cloves, finely chopped; 2 Tbsp. finely chopped thyme; ½ cup all-purpose flour; 5 cups whole milk; 2 Tbsp. Dijon mustard; 2 tsp. finely grated lemon zest; 1 large egg; 6 oz. Parmesan, finely grated (about 3 cups); 2 cups whole-milk fresh ricotta; 8 oz. low-moisture mozzarella, coarsely grated (1⅓ cups)

Ingredients

1 lb. dried lasagna
3½ tsp. Diamond Crystal or 2 tsp. Morton kosher salt, divided, plus more
16 Tbsp. (2 sticks) unsalted butter, divided
2 lb. crimini mushrooms, trimmed, thinly sliced
1½ tsp. freshly ground pepper, divided, plus more
3 shallots, finely chopped
8 garlic cloves, finely chopped
2 Tbsp. finely chopped thyme
½ cup all-purpose flour
5 cups whole milk
2 Tbsp. Dijon mustard
2 tsp. finely grated lemon zest
1 large egg
6 oz. Parmesan, finely grated (about 3 cups)
2 cups whole-milk fresh ricotta
8 oz. low-moisture mozzarella, coarsely grated (1⅓ cups)

Steps

Place a rack in middle of oven; preheat to 375°. Cook 1 lb. dried lasagna in a large pot of generously salted water, stirring occasionally, until about 3 minutes shy of al dente (it should be about two thirds of the way cooked and still slightly too hard to eat), about 5 minutes. Drain pasta, rinse under cold running water until cool to the touch, and set aside.
Meanwhile, melt 6 Tbsp. unsalted butter in a large Dutch oven or other heavy pot over medium-high heat. Add 2 lb. crimini mushrooms, trimmed, thinly sliced, 1 tsp. Diamond Crystal or ½ tsp. Morton kosher salt, and ½ tsp. freshly ground pepper. Cook, stirring often, until mushrooms release their moisture, shrink, and brown, 15–20 minutes. Transfer to a large bowl; reserve pot.
Melt remaining 10 Tbsp. unsalted butter in reserved pot over medium heat. Cook 3 shallots, finely chopped, 8 garlic cloves, finely chopped, and 2 Tbsp. finely chopped thyme and cook, stirring often, until shallots are softened to an almost paste-like texture and mixture is fragrant, 7–10 minutes. Add ½ cup all-purpose flour, 2½ tsp. Diamond Crystal or 1½ tsp. Morton kosher salt, and 1 tsp. freshly ground pepper and cook, stirring constantly, until onions are evenly coated in flour and no dry pockets remain, 1–2 minutes. Gradually pour in 5 cups whole milk, whisking constantly, and bring to a simmer. Cook, whisking constantly, just until thick enough to coat a spoon, 1–2 minutes. Stir in 2 Tbsp. Dijon mustard and 2 tsp. finely grated lemon zest. Taste sauce and season with more salt and pepper if needed.
Combine 1 large egg, 6 oz. Parmesan, finely grated (about 3 cups), and 2 cups whole-milk fresh ricotta in a medium bowl; season cheese mixture with salt and pepper. Spread about ¾ cup sauce across the bottom of a 13×9" glass or ceramic baking dish. Top with an even layer of noodles (about 3½). Cut in half lengthwise as needed to puzzle in tightly. (If noodles are sticking together, rinse under cool running water to help unstick.) Spread a heaping ⅓ cup cheese mixture over noodles, scatter a heaping ⅓ cup mushrooms evenly on top, and dollop a heaping ⅓ cup sauce on top. Starting with noodles, repeat layers, using more or less of various components depending on how quickly you deplete them. Spread final sauce layer (about ½ cup) thinly and evenly over mushrooms, then sprinkle 8 oz. low-moisture mozzarella, coarsely grated (1⅓ cups) evenly on top.
Bake lasagna until edges are golden brown and bubbling, 40–50 minutes. If you’d like additional color on top, heat broiler and broil just until center is browned (keep a close eye on lasagna to prevent burning), 1–3 minutes, depending on your broiler. Let lasagna sit 15 minutes before serving. Do Ahead: Lasagna can be assembled 1 day ahead. Cover and chill. Baking time will be 5–10 minutes longer.