In a casserole dish, add potatoes, garlic, thyme, bay leaf, and kosher salt; toss to combine. Pour olive oil over the potato mixture, should be enough to cover the potatoes. Cover the pan loosely with foil and bake for two hours or until the potatoes are tender enough to be pierced with a knife.
Let potatoes rest in the oil until they are at room temperature.
When cool, remove the potatoes from the oil mixture, and carefully peel the skin from the potatoes.
While the potatoes are cooling, reduce chicken stock by about 90% to a ‘glace’ consistency that coats the back of a spoon. Add vinegar, mustard, salt, and pepper, to the chicken glace to create a marinade. Add the peeled potatoes to the marinade.
Mix and cook for two minutes, then cover with tinfoil.
Preheat oven to 300F (150C).
Place the pan of marinated potatoes in the oven. Bake the pan of potatoes for twenty minutes.
Remove from the oven, garnish with chives, and serve