2. Set a chicken breast on a flat surface. With your fingers, gently push a pocket under the skin from beside the wing bone up over the top of the breast. Do not remove the skin entirely. Take 1 or 2 tbsp. of the mushroom mixture and gently push it into the little pocket. Don’t force too much in. The pocket should hold at least 1 to 2 tbsp., depending on the breast size. Secure the pocket with a toothpick and press down lightly to adhere seasoning mixture and skin to the breast. Cover the stuffed breasts and refrigerate for 1 hour.
3. For the Vinagrette -In a saucepan, heat the 2 tbsp. mushrooms, ¼ cup Garlic and Herb Rub, and 2 tsp. sage over medium-high heat, stirring frequently. When thoroughly heated, add the orange juice, vinegar, and the oil and remove from the heat. Season with salt and pepper to taste. Set aside at room temperature.
4. For Grilling: Preheat the grill to medium (350ºF/175ºC). Brush the inside of the basket with oil. Secure chicken breasts in the basket. Grill, skin side down first, brushing with the vinaigrette, about 8 to 10 minutes a side, or until a meat thermometer inserted into the thickest part of the breast registers 160ºF (71ºC).
5. When done, remove the breasts very carefully from the basket, keeping the skin and stuffing intact. Serve the breasts with the vinaigrette, either whole or sliced and fanned on the plate.