Preheat the oven to 325F. Then mix the spices together with the salt to make a rub.
Sprinkle the spice mix over the chicken breasts and pat it to get the rub to stick nicely to the chicken.
Drizzle olive oil into a casserole dish and place the chicken into the dish.
Pour in the chicken stock and then place the pats of butter around the chicken. Toss the rosemary sprigs into the casserole dish too.
Cover the dish with aluminum foil and then place in the oven to bake for 60 minutes. Take it out every 20 minutes or so and use a spoon to pour the butter and chicken over the breasts to baste them.
Remove the foil and baste the breasts again before serving them.