Preheat oven to 200ºC (400ºF). Melt 2 tbsp (30 mL) butter in skillet over medium heat. Stir in Swiss chard, leeks, sage, 1/4 tsp (1 mL) each salt and pepper ; cook 5 min. until vegetables are tender. Transfer to large bowl to set aside to cool completely.
Meanwhile, place turkey breast -- with underside facing up -- on cutting board. Use a sharp knife to make small horizontal cuts into the thicker parts of the meat, “unfolding” the cuts as you go to create a thinner slab of meat roughly rectangular in shape. Cover the meat with plastic wrap and pound to 1/2-in. (1-cm) thickness.
Add rice, 2 tbsp (30 mL) broth, lemon zest and lemon juice to chard mixture. Mix well. Toss in egg and cheese. Spread stuffing onto pounded turkey breast, leaving a 1-in. (2.5-cm) border. Starting from the long end, tightly roll up turkey into a log, tucking in ends to enclose filling. Tie up with butcher’s twine. Rub surface with remaining butter; season with remaining salt and pepper. Place turkey roll on rack in roasting pan. Pour 1 cup (250 mL) broth into bottom of pan. Roast 40 to 45 min., or until instant-read thermometer reaches 74ºC (165ºF). Transfer turkey roll to clean cutting board. Tent with foil to rest 15 min.
Meanwhile, place roasting pan over medium-high heat. Stir in remaining broth, scraping pan to incorporate browned bits into sauce. Bring to a boil. Mix together cornstarch and 2 tbsp (30 mL) water until smooth. Whisk into sauce; bring back to a boil. Reduce heat to medium-low; simmer 6 to 8 min., or until thickened to desired consistency. Stir in parsley. Remove butcher’s twine from roll. Slice and serve turkey with pan gravy.
To save time use prepared, ready-cooked brown rice pouch, or use leftover quinoa or wild rice.