Sweet Pea Casserole

Ingredients

• ¼ cup Butter
• 1 (8-ounce) container sliced fresh baby portobello mushrooms
• 1 cup chopped onion
• 2 cloves garlic, minced
• 2 tablespoons All-purpose flour
• 1 teaspoon sugar
• ¾ teaspoon salt
• ¼ teaspoon ground black pepper
• ⅛ teaspoon Ground nutmeg
• 2 cups half-and-half
• 1 cup shredded Swiss cheese
• 1 cup shredded Parmesan cheese
• 2 (16-ounce) packages frozen peas, thawed and drained
• 1 (2.8-ounce) can french-fried onion rings