1. Cut the turkey breasts into cubes.
Peel and slice the onion and garlic.
Remove the stems from the mushrooms, and quickly rinse them before cutting them in half.
2. Heat the oil in a Dutch oven and sauté the onion for 2 minutes.
Add the turkey pieces and brown them on all sides.
Season with salt, pepper, add the mushrooms, garlic, bouquet garni, and then the broth.
3. Bring to a boil, then reduce the heat and let simmer for 20 minutes.
4. Peel the celeriac, rinse it, and cut it into small cubes.
Steam for 5 minutes.
Add them to the Dutch oven with the cream, mix well, then serve the blanquette.