How to Make It
Preheat the oven to 400°. In a large bowl, toss the chicken pieces with the olive oil, Parmesan cheese, oregano and garlic. Arrange the chicken pieces, skin side up, on a large rimmed baking sheet and season with salt and pepper. Bake for about 45 minutes, or until lightly browned and just cooked through.
Meanwhile, in a small saucepan, combine the chicken stock and vinegar and boil over high heat until reduced to 1/3 cup, about 10 minutes. Remove from the heat and whisk in the butter, 1 tablespoon at a time, until smooth. Season with salt and pepper. Transfer the chicken to plates, spoon the sauce on top and serve.