Halve peppers lengthwise; discard seeds and membrane. Cook peppers, uncovered, in boiling water for 3 to 5 minutes; invert on paper towels to drain well.
In a skillet cook ground turkey, leek, and garlic until turkey is brown and leek is tender. Drain off any fat. Stir in chopped tomatoes, mushrooms, uncooked rice, water, parsley, basil, bouillon granules, and hot pepper sauce. Bring to boiling; reduce heat. Cover and simmer about 15 minutes or until rice is tender. Place pepper halves in an 8x8x2-inch baking dish. Fill each pepper half with some of the turkey-rice mixture.
Bake, covered, in a 350 degree F. oven for 30 to 35 minutes or until heated through. Top each pepper with a cheese triangle. Serve immediately. Makes 4 main-dish servings.