Chop the sweet potatoes into 1-inch cubes. Put them into a 2-quart pot and cover them with water. Boil the sweet potatoes for 20 minutes or until a fork inserted into a cube breaks it in half easily.

Chop the onion and begin browning it in oil. Add the ground goat, salt, coriander, and garam masala. Stir the meat frequently to prevent burning until it is cooked thoroughly. Add the cooked sweet potatoes to the pan, and stir the cubes into the meat mixture.

In a bowl, mix together the yogurt, lemon juice, and garlic.

To serve, put the meat and sweet potato mixture on a plate and drizzle it with the yogurt sauce.