Try our vegetarian rendition of this classic grilled sandwich.
Heat 1 tablespoon oil in skillet over medium heat. Add garlic and onion; cook until translucent, 2 to 3 minutes. Add red pepper, thyme, and oregano. Add bell pepper; saute until soft, about 5 minutes. Transfer to bowl.
Add 3 tablespoons oil to skillet. Add egg-plant and squash; saute until soft, 5 to 7 minutes. Add tomatoes and wine, and raise heat to medium high; cook, stirring, until liquid simmers away, 8 to 10 minutes. Add 3/4 teaspoon salt, 1/2 teaspoon pepper, and chopped parsley. Toss with onions and peppers. Adjust seasoning with salt, pepper, and dried herbs.
Heat oven to 350 degrees. Whisk eggs and milk in shallow bowl; add remaining 1/4 teaspoon salt and 1/4 teaspoon pepper. Sprinkle half the cheese and spread ratatouille over eight slices of bread. Cover filling with remaining cheese; close sandwiches with remaining bread.
Heat 1 tablespoon oil in large skillet over medium-high heat. Coat two sandwiches, one at time, with egg batter. Place sprig of parsley on bread; saute, parsley side down, in skillet, until golden and puffy, and cheese is just starting to melt, 2 to 3 minutes. Turn; cook until golden and melted, 2 to 3 minutes. Place in oven 5 to 7 minutes so batter is cooked through and filling is hot. Repeat process. Keep sandwiches warm in oven.