Heat the olive oil in a large pan over medium heat.
Add the onion, garlic, carrot, and celery. Sauté for about 5 minutes until softened.
Add the chopped mushrooms and cook until they start to release moisture and turn golden.
Stir in the tomato paste and thyme. Mix well to coat the vegetables.
Pour in the vegetable broth and bring to a simmer.
Add the cooked lentils and cream, stirring gently.
Simmer uncovered for about 15 minutes, until the sauce thickens slightly.
Season with salt and pepper to taste.
Serve warm, topped with fresh parsley and a slice of crusty bread or pasta.