Combine broth and soymilk in large saucepan; blend in flour, salt and garlic. Stir in potatoes. Bring to boil, stirring constantly. Reduce heat and simmer for 3 minutes. Pour mixture into 2 quart casserole or au gratin dish; dot evenly with butter. Place dish on baking sheet and bake at 400˚F for 1 hour, or until potatoes are tender.