White Sauce Lasagna with Spinach and Mushrooms

By AislePrompt Test Kitchen · Reviewed by AislePrompt Editorial · Published 2026-06-02 · Updated 2026-06-02

Layers of tender pasta sheets with sautéed spinach and mushrooms enveloped in a smooth béchamel white sauce and melted mozzarella. This italian-inspired pasta (vegetarian) ready in about 70 minutes blends sheets lasagna noodles, unsalted butter, all-purpose flour into a versatile sauce that lifts everything from grain bowls and roasted vegetables to grilled proteins — a small-batch staple worth keeping in the fridge. Each serving lands at about 400 calories and feeds 6, so a small batch covers several meals across the week without taking over the fridge. Tap "Plan a meal with the AI" below to drop this recipe into your week and send the ingredients straight to Instacart. Nutrition values are approximate, calculated from USDA FoodData Central (fdc.nal.usda.gov) — verify against ingredient labels for any health-driven dietary plan.

Ingredients

• 9 sheets lasagna noodles
• 4 tbsp unsalted butter
• 4 tbsp all-purpose flour
• 3 cups whole milk
• 1/4 tsp nutmeg, ground
• 6 cups fresh spinach, roughly chopped
• 8 oz cremini mushrooms, sliced
• 2 tbsp olive oil
• 2 garlic cloves, minced
• 2 cups mozzarella cheese, shredded
• 1/2 cup Parmesan cheese, grated
• to taste salt
• to taste black pepper

Instructions

1. Step 1: Preheat oven to 350°F. Bring a large pot of salted water to a boil and cook 9 lasagna noodles for 8 minutes until al dente. Drain and lay flat on a towel.
2. Step 2: In a medium saucepan, melt 4 tbsp unsalted butter over medium heat. Whisk in 4 tbsp all-purpose flour and cook for 1-2 minutes until mixture bubbles and is lightly golden.
3. Step 3: Gradually whisk in 3 cups whole milk, continuing to whisk until sauce thickens and coats the back of a spoon, about 6-8 minutes. Stir in 1/4 tsp ground nutmeg, salt, and black pepper to taste. Remove from heat.
4. Step 4: Heat 2 tbsp olive oil in a skillet over medium heat. Add 2 minced garlic cloves and sauté for 30 seconds until fragrant.
5. Step 5: Add 8 oz sliced cremini mushrooms and cook for 5 minutes until they release moisture and start to brown.
6. Step 6: Add 6 cups chopped fresh spinach to the skillet and cook until wilted, about 3 minutes. Season with salt and pepper, then remove from heat.
7. Step 7: Spread a thin layer of the white sauce on the bottom of a 9x9 inch baking dish. Layer 3 lasagna noodles over sauce, then half of the spinach-mushroom mixture, 1/3 of the remaining white sauce, and 2/3 cup shredded mozzarella.
8. Step 8: Repeat layering with 3 noodles, remaining spinach mixture, 1/3 white sauce, and 2/3 cup mozzarella.
9. Step 9: Top with last 3 noodles, remaining white sauce, 2/3 cup mozzarella, and 1/2 cup grated Parmesan cheese.
10. Step 10: Cover loosely with foil and bake at 350°F for 30 minutes. Remove foil and bake an additional 10 minutes until cheese is golden and bubbly.
11. Step 11: Let rest for 10 minutes before slicing and serving.