Peel and slice the onions into thin rings.

Heat a large skillet over medium heat and add butter.

Once the butter has melted, add the onions to the skillet and stir to coat them with butter.

Cook the onions for about 30-40 minutes, stirring occasionally, until they are caramelized and golden brown.

The soup is the heart of the French Onion soup casserole, and it's important to get it right. Here's how you can make the soup:

In a large pot, melt butter over medium heat.

Add flour and whisk until smooth.

Gradually add vegetable broth and whisk until the mixture is smooth as you heat the soup.

Add thyme, bay leaf, salt, and pepper to the pot.

Bring the soup to a boil, then reduce the heat and let it simmer for 20-30 minutes.

The topping is what makes the French Onion soup casserole so delicious. Here's how you can prepare it:

Preheat the oven to 375°F.

In a small bowl, mix together breadcrumbs, grated Parmesan cheese, and melted butter.

Layer onions in the bottom of a casserole dish.

Pour soup mixture over the onions.

Place crusty bread slices on top of the soup. Push bread lightly into the soup. Sprinkle the cheese mixture over the top of bread.

Bake the casserole for 25-30 minutes, or until the topping is golden brown and crispy.

Top with vegan cream cheese and a garnish of fresh herbs and serve.

By following these simple steps, you can make a delicious French Onion soup casserole that's sure to impress your family and friends.

In a large skillet or Dutch oven, melt the butter or heat the olive oil over medium heat. Add the sliced onions and sauté for about 25-30 minutes until caramelized, stirring occasionally.

Add the minced garlic and balsamic vinegar to the skillet and cook for an additional 1-2 minutes, until fragrant.

Sprinkle the flour over the onions and stir to coat evenly. Cook for 1-2 minutes to cook off the raw flour taste.

Optional: If using red wine, add it to the skillet and cook for 2-3 minutes to allow the alcohol to evaporate.

Slowly pour in the vegetable broth, stirring constantly to prevent lumps from forming. Add the soy sauce, dried thyme, salt, and pepper. Bring the mixture to a simmer and cook for 10-15 minutes to allow the flavors to meld together.

Preheat your oven to 400°F (200°C).

Ladle the onion soup into an oven-safe casserole dish. Arrange the toasted bread slices on top of the soup, covering it completely.

Sprinkle the shredded Gruyere or Swiss cheese over the bread slices, making sure to cover them evenly.

Place the casserole dish in the preheated oven and bake for about 15-20 minutes until the cheese is melted and bubbly.

Remove the casserole from the oven and let it cool slightly before serving. Garnish with fresh thyme leaves, if desired.

Enjoy the comforting and flavorful vegetarian French onion soup casserole for 4 people!

Set your Instant Pot to "Sauté" mode and add the butter or olive oil. Once heated, add the thinly sliced onions and sauté for about 10 minutes until they become soft and caramelized.

Add the minced garlic and continue sautéing for another minute until fragrant.

Stir in the balsamic vinegar and cook for a minute to deglaze the pot.

Sprinkle the flour over the onion mixture and stir well to coat the onions evenly.

If using red wine, add it to the pot and stir for a minute to allow the alcohol to cook off.

Pour in the vegetable broth and soy sauce. Add the dried thyme, salt, and pepper to taste. Give it a good stir to combine all the ingredients.

Cancel the "Sauté" mode and close the Instant Pot lid. Set it to "Manual" or "Pressure Cook" mode on high pressure for 10 minutes.

Once the cooking time is complete, allow for a natural pressure release for about 10 minutes, then do a quick release to release any remaining pressure.

Carefully open the lid and give the soup a stir. Adjust the seasoning if needed.

Preheat your oven's broiler. Ladle the soup into oven-safe bowls or crocks, leaving some space at the top. Place a slice of toasted crusty bread on top of each bowl and sprinkle with shredded Gruyere or Swiss cheese.

Place the bowls on a baking sheet and transfer them under the broiler until the cheese is melted and bubbly, usually around 2-3 minutes.

Remove from the oven and let the soup cool slightly before serving. Garnish with fresh thyme leaves if desired.

Enjoy your delicious homemade French onion soup made in the Instant Pot!

Heat a skillet or stovetop-safe slow cooker insert over medium heat. Add the butter or olive oil and melt it. Once heated, add the thinly sliced onions and sauté for about 10 minutes until they become soft and caramelized.

Add the minced garlic and continue sautéing for another minute until fragrant.

Stir in the balsamic vinegar and cook for a minute to deglaze the pan.

Sprinkle the flour over the onion mixture and stir well to coat the onions evenly.

If using red wine, add it to the skillet and stir for a minute to allow the alcohol to cook off.

Transfer the onion mixture to the crockpot or slow cooker. Add the vegetable broth, soy sauce, dried thyme, salt, and pepper. Stir to combine all the ingredients.

Cover the crockpot or slow cooker and cook on low heat for 6-8 hours or on high heat for 3-4 hours. This slow cooking process will allow the flavors to meld together.

Once the soup has finished cooking, taste and adjust the seasoning if needed.

Preheat your oven's broiler. Ladle the soup into oven-safe bowls or crocks, leaving some space at the top. Place a slice of toasted crusty bread on top of each bowl and sprinkle with shredded Gruyere or Swiss cheese.

Place the bowls on a baking sheet and transfer them under the broiler until the cheese is melted and bubbly, usually around 2-3 minutes.

Remove from the oven and let the soup cool slightly before serving. Garnish with fresh thyme leaves if desired.