The sweet potato leaves are typically dried and pounded well before cooking, not used fresh, which changes both their texture and how long the dish keeps.
Dried, crushed sweet potato leaves (kalembula) are sautéed with sliced impwa eggplant, onion, tomato and a little oil until soft, making a hearty two-vegetable relish. It's a common, budget-friendly plate at Copperbelt nsima places.