Sprinkle lamb pieces with salt.
Cook lamb, in batches, in a Dutch oven coated with cooking spray over medium-high heat, stirring often, 5 minutes or until lamb is lightly browned. Remove and set aside.
Sauté onion and ginger in a Dutch oven coated with cooking spray over medium-high heat 1 to 2 minutes. Add garlic; cook 1 minute. Stir in coriander and next 4 ingredients. Add cooked lamb, broth, and tomatoes; bring to a boil. Cover, reduce heat, and simmer 1 hour or until lamb is tender. Remove from heat; add yogurt and garam masala, stirring until blended. Sprinkle with mint.