To prepare sauce, combine cornstarch and water in small bowl, stirring with a whisk to form a slurry. Bring vinegar and sugar to a simmer in small saucepan, stirring until sugar dissolves. Add slurry mixture; simmer 2 minutes or until slightly thickened, stirring constantly with a whisk. Remove from heat. Stir in mint and curry powder; steep 30 minutes. Strain and set aside.
Preheat oven to 450°.
To prepare lamb, place bread in a food processor, and pulse 10 times or until coarse crumbs measure 1 cup. Combine breadcrumbs, garam masala, 1/2 teaspoon salt, and 1/2 teaspoon pepper in a small bowl. Place lamb on a shallow baking sheet. Press breadcrumb mixture onto lamb. Bake at 450° for 15 minutes or until desired degree of doneness.