Heat oil in a large pot over medium-high heat. Add onion and cook, stirring occasionally, until softened, 3 minutes. Add garlic, chile, 1 tsp. salt, and the spices; cook 2 minutes longer. Stir in tomato paste.
Add lamb and cook, breaking up large chunks of meat, until no longer pink, about 3 minutes. Add potatoes, yogurt, and milk to pan and bring to a boil. Reduce heat until mixture is simmering vigorously, cover, and cook 10 minutes.
Stir in peas and cook 5 minutes longer, until peas are cooked through and mixture has thickened. Serve over rice with cilantro sprinkled on each serving. Add more salt to taste if you like.
Note: Nutritional analysis is per serving.