1 lemon
2 yellow onions, cut into 2-inch chunks
2 pound(s) baby potatoes (also called new potatoes or creamers), halved (or left whole if really tiny)
1/4 cup(s) whole-grain Dijon mustard, such as Maille
3/4 cup(s) extra virgin olive oil
1 1/2 teaspoon(s) fresh rosemary leaves, finely chopped
2 sprig(s) fresh rosemary
1 tablespoon(s) fresh thyme leaves, roughly chopped
4 sprig(s) fresh thyme
Kosher salt
Freshly ground black pepper
1 whole(s) (4- to 5-pound) roasting chicken
1 bay leaf
2 or 3 clove(s) garlic
3 tablespoon(s) unsalted butter, at room temperature