Mashua (Tropaeolum tuberosum) is a stem tuber from a climbing relative of the garden nasturtium, the fourth of the great Andean tuber crops grown alongside the potato, oca and ulluco. Its conical, deeply ridged tubers shade from waxy white and yellow through orange to red and purple, and carry a sharp, peppery, mustard-like bite that mellows with sun-curing and cooking.