Preheat oven to 350 F (180 C)
Season chicken the mustard, onion, garlic, salt and pepper, let this marinate at least 30 minutes.
In a large pan (Dutch oven) heat the olive oil and brown your chicken on every side, when is all golden brown, add the potatoes, the stock and the thyme, cover and cook in the oven for 35 minutes.
Plate chicken and potatoes and pour the sauce over them. Enjoy!
NOTES
If you want you can add a tablespoon of butter to the liquid on the bottom of the pan to bring all the flavors together, if you don't want any pieces on the sauce, you can strain it before serving.