Heat the oven to 300 degrees. Evenly salt the turkey breast with 1 1/2 teaspoons of kosher salt. Set aside.
Heat the butter and prosciutto over medium high heat. Once the butter is melted, the fat rendered from the prosciutto and the pan is hot, remove the prosciutto and set aside (to be used later). Place the turkey into the skillet and brown, about 3 minutes per side (for a total of six minutes).
While the turkey is browning, add the onion, apple, garlic, herbs and cinnamon stick. Continue to cook these items for about 1 minute after the removal of the turkey. Stir occasionally.
Reduce the heat to medium and add the cognac and scrape up the brown bits on the pan. Let the cognac simmer for 30 seconds to 1 minute. Add the milk, remaining 1/2 teaspoon kosher salt and the turkey breast. Bring the milk to a low simmer. Cover the breast with the cooked prosciutto and baste once. Place in the oven.
Cook the turkey for 45-55 minutes, or until the turkey reaches 160 degrees. Baste every 15 minutes. Slice and serve warm with the milk sauce.
The cooking time varies depending on the size of the turkey breast. This recipe also works well with a halved boneless turkey breast. The cook time for a boneless breast is 30 minutes.