Heat the olive oil in a large pot over medium heat. Add the onion and carrots and cook for 5 minutes until the onion turns soft.
Stir in the garlic and mushrooms. Cook for another 4 minutes until the mushrooms release their liquid and start to brown.
Add the tomato paste, herbes de Provence, and thyme. Stir for 1 minute to coat the vegetables.
Pour in the vegetable broth and add the lentils, bay leaf, salt, and pepper. Bring the mixture to a boil.
Reduce the heat to low, cover the pot, and simmer for 30 minutes until the lentils are tender.
Remove the bay leaf and stir in the fresh parsley just before serving.