6 bone-in, skin-on chicken breast halves (about 12 ounces each), trimmed of excess fat and skin
Table Salt for brine
Vegetable Oil for cooking grate
6 Tbsp. unsalted butter, softened
1 med-large shallot, minced (about 4 1/2 Tbsp.)
2 Tbsp. chopped fresh sage
3 ounces fontina cheese, rind removed, cut into four 3 by 1/2-inch sticks
6 thin slices prosciutto (about 3 ounces)
Ground black pepper
1. Starting on thick side of breast, closest to breastbone, cut horizontal pocket in each breast, stopping 1/2 inch from edge so halves remain attached. Dissolve 4 1/2 Tbsp. salt in 1 1/2 quarts cold water in large container. Add breasts, cover with plastic wrap, and refrigerate 30 minutes.
2. Combine butter, shallot and sage in small bowl. Roll each piece of cheese in 1 slice of prosciutto. Remove breasts from brine, dry thoroughly inside and out with paper towels and season inside and out with pepper. Spread equal amount of butter mixture inside each breast. Place 1 prosciutto-wrapped piece of cheese inside each breast and fold breast over to enclose. Evenly space 3 pieces kitchen twine (each about 12 inches long) beneath each breast and tie, trimming any excess.
To prepare for freezing:
Follow all instructions above. Wrap each breast individually in cling wrap then place in freezer bag. Thaw in refrigerator before grilling and carefully remove wrap so as not to disturb twine ties and stuffing.
If using charcoal grill (recommended):
1. Light large chimney starter filled with charcoal (6 quarts, about 100 briquettes) and allow to burn until coals are fully ignited and partially covered with thin layer of ash, about 20 minutes. Arrange all coals over half of grill, leaving other half empty. Position cooking grate over coals, cover grill, and heat grate until hot, about 5 minutes. Scrape grate clean with grill brush. Dip wad of paper towels in vegetable oil; holding wad with tongs, wipe cooking grate. Grill is ready when coals are hot (you can hold your hand 5 inches above grate for 2 seconds).
2. Place chicken breasts, skin side down, over hot part of grill and cook until well browned, 3-5 minutes. Flip chicken and cook until second side is just opaque, about 2 minutes. Move chicken, skin side up, to cool side of grill, with thicker side of breasts facing fire. Cover grill and continue to cook until instant-read thermometer inserted into thickest part of stuffing registers 160 degrees, 25-30 minutes. Transfer chicken to carving board and let rest, tented with foil, 10 minutes. Remove twine, then, if desired, carve breast meat from bone and cut into 1/2-inch-thick slices.
If using gas-grill:
1. Turn all burners to high, close lid, and heat until hot, about 15 minutes. Scrape grate clean with grill brush. Dip wad of paper towels in oil; holding wad with tongs, wipe cooking grate. Leave primary burner (burner that will stay on during grilling) on high and turn off other burner(s). Proceed with recipe step 2 from charcoal instructions, cooking chicken with lid closed and increasing cooking time on cooler side of grill to 30-40 minutes.
Note: May also prepare stuffed with Black Forest Ham and Gruyere - substitute 1 1/2 tsp. minced fresh thyme for sage and add 1 1/2 Tbsp. Dijon mustard to butter in step 2. Substitute 6 slices Black Forest Ham for prosciutto and Gruyere cheese for fontina.