From thighs, remove and discard skin and bones (reserve for stockpot); set thigh meat aside.

Break shiitake mushrooms into small pieces and, in spice grinder, grind into fine powder; mix together with five-spice powder, sage, salt and pepper and set aside.

At intervals of about 1-1/2 inch/4 cm, lay 7 or 8 lengths of kitchen string, each about 18 inches/45 cm long, on work surface. Place turkey breast, skin side down, across strings, shaping meat to as even a thickness as possible. Brush with 2 tbsp/30 mL of the butter; sprinkle with 1 tbsp/15 mL of the mushroom mixture. Lay thigh meat on top; sprinkle with 1 tbsp/15 mL of the mushroom mixture. Roll each long edge of breast toward centre; tie into roast. Sprinkle remaining mushroom mixture all over.

Brush roasting pan with 2 tbsp/30 mL of the butter; place ginger slices on bottom of pan and top with roast, seam side up. Brush with remaining butter. Roast in 325F/160C oven for 1 hour. Turn roast seam side down; baste with sherry.

Continue roasting, basting with pan juices every 15 minutes, until thermometer inserted in centre of roast registers 165F/74C or juices run clear when roast is pierced, about 1-1/2 hours (check about 15 minutes before end of roasting; if skin isn't crisp, increase oven temperature to 375F/190C).

Transfer roast to serving platter; keep warm in oven with door ajar (do not tent with foil or skin will lose crispness).

Skim off 1/4 cup/60 mL of the fat from pan juices and transfer to saucepan.

Skim off and discard remaining fat; through fine sieve, strain juices into 4-cup/1 L heatproof measuring cup and add enough stock to make 4 cups/1 L. Return 1 cup/250 mL stock mixture to roasting pan over medium heat and bring to boil; deglaze pan, scraping up brown bits from bottom and sides. Return to measuring cup with stock mixture.

Heat fat in saucepan over medium heat; stir in flour and cook, stirring, for 2 minutes. Whisk in stock mixture; bring to boil, stirring. Reduce heat to simmer; stir in soy sauce. Finely slice white and light green parts of onions and add; simmer, stirring often, for 3 minutes. Slice dark green parts of onions; discarding remainder, stir 2 tbsp/30 mL into gravy.

Slice turkey; serve gravy on side.

Makes 12 servings.