Cheesy Meatless Stuffed Shells

Ingredients

• 18 piece (blank)s jumbo pasta shells
• 2 tablespoons olive oil
• 1 (12 ounce) package meatless ground beef substitute (such as Impossible(TM) Foods)
• 1 (15 ounce) can fire-roasted diced tomatoes
• ½ medium onion, diced
• 2 teaspoons minced garlic
• 1 tablespoon Italian seasoning
• salt and ground black pepper to taste
• 3 cups loosely packed fresh spinach
• 1 (15 ounce) container ricotta cheese
• 1 large egg, beaten
• 1 (24 ounce) jar marinara sauce
• 1 cup shredded Parmesan cheese
• 1 cup shredded mozzarella cheese
• ¼ teaspoon Italian seasoning or to taste