Vegetarian Bourguignon with Mushrooms and Lentils

Preheat oven to 325°F (160°C).

Heat olive oil in a large oven-safe pot or Dutch oven over medium-high heat. Add mushrooms and cook until browned and softened, about 8-10 minutes. Remove mushrooms from the pot and set aside.

Add onion, carrots, and celery to the pot and cook until softened, about 5-7 minutes. Add garlic and cook for 1 minute more, until fragrant.

Stir in tomato paste and cook for 1 minute.

Sprinkle flour over the vegetables and cook for 1 minute, stirring constantly.

Pour in red wine and bring to a simmer, scraping up any browned bits from the bottom of the pot.

Add vegetable broth, thyme, bay leaf, and lentils. Bring to a boil, then reduce heat to low, cover, and simmer for 30 minutes.

Stir in the reserved mushrooms and pearl onions (if using). Season with salt and pepper to taste.

Cover the pot and transfer it to the preheated oven. Braise for 1 hour, or until the lentils are tender and the sauce has thickened.

Remove from oven and let rest for 10 minutes before serving. Remove bay leaf before serving.

Garnish with fresh parsley and serve hot with mashed potatoes or crusty bread.