Heat a 12-inch cast-iron skillet over medium-high heat and add the oil. Once the oil begins to smoke add the chicken and brown well, stirring often to cook evenly without sticking to the bottom of the pan.
Add the garlic and shallots and brown slightly taking care not to burn. Add the mushrooms, salt, and pepper and cook stirring constantly for 1 minute or until the mushrooms are tender.
Add the chicken stock and bring to boil and then stir in the chopped rosemary, whole rosemary sprig, and paprika.
In a small dish combine the cornstarch and cold water and stir into the pan. Stir until the sauce is thickened. Taste and season with salt and pepper if needed.
Sprinkle with parsley and serve.
