Swiss Chard Spanakopita Casserole Recipe

Ingredients

• Cooking spray
• 2 1/4 cups minced white onion
• 3/4 cup minced green onions
• 3 garlic cloves, minced
• 9 cups chopped trimmed Swiss chard (about 1 1/2 pounds)
• 6 tablespoons chopped fresh parsley
• 3 tablespoons minced fresh mint
• 1 cup (4 ounces) crumbled feta cheese
• 1/2 cup (2 ounces) freshly grated Parmesan cheese
• 1/2 teaspoon salt
• 1/4 teaspoon black pepper
• 3 large egg whites
• 10 (18 x 14 inch) sheets frozen phyllo dough, thawed