Preheat oven to 425 degrees F.
Mix cornmeal, flour, baking powder, sour cream, milk, eggs, salt and melted butter. Bake in a greased loaf pan for 20 to 25 minutes until golden brown and when a toothpick inserted into center comes out clean. Let cool in pan.
Let oven temperature reduce to 400 degrees F.
For the Turkey:
Rinse turkey breast and pat dry with paper towels. Slip chunks of butter under the skin. Season turkey breast with garlic powder, salt and pepper, to taste, and roast in 400 degrees F oven until it reaches an internal temperature of about 160 degrees F on an instant-read thermometer, about 1 1/2 to 2 hours.
For the Dressing:
Heat oil in a large skillet over medium heat. Saute sausage until browned. Remove to a utility platter with a slotted spoon and pour most of the fat from the pan leaving about 1 tablespoon. Melt butter in the skillet over medium heat. Saute onion, garlic, celery, parsley, sage and thyme until onion is translucent, being careful not to burn them. Remove from heat and set aside briefly. Cut cornbread into cubes or break it up with your hands into a large bowl (depending on the texture you like). Spoon the sauteed vegetables and herbs over the cornbread. Stir or use your hands to combine well and add enough chicken stock to moisten. Transfer to a baking pan and place in the oven until crispy on the outside, for approximately the last 25 minutes of the turkey's roasting time. Remove from oven and transfer to a serving dish in a warm place.
For the Gravy:
When turkey is done, remove breast to a platter to let rest for 20 minutes before slicing. Skim most of the fat from the pan juices, reserving 1/3 cup of the fat. Add wine to the remaining pan juices and cook over medium-high heat until reduced by half. In a separate saucepan, heat reserved 1/3 cup of fat and whisk in flour over moderately-low heat for a few minutes to make a roux. Add chicken stock and reduced wine, continuing to cook until gravy simmers.
Slice turkey and arrange on plate. Serve with cornbread dressing and gravy.