Creamy Baked Pasta with Green Beans and Mushrooms

Ingredients

• 12 oz short pasta (penne or rigatoni)
• Salt, for boiling
• 12 oz fresh green beans, trimmed and cut into 1-inch pieces
• 8 oz cremini or button mushrooms, sliced
• 1 medium yellow onion, diced
• 2 cloves garlic, minced
• 4 tbsp unsalted butter
• 1/4 cup all-purpose flour
• 2 1/2 cups whole milk
• 1/2 cup vegetable broth
• 1/2 cup grated Parmesan cheese
• 1/2 tsp dried thyme
• 1/2 tsp ground black pepper
• 1/2 tsp salt (plus more to taste)
• 1/4 tsp ground nutmeg
• 1 1/2 cups crispy fried onions
• 1/2 cup grated sharp cheddar cheese (optional)