Potato Gypsy’s Arm

Brazo de gitano, or gypsy’s arm, is the picturesque Spanish term for a jelly roll. Most are sponge cake–based sweets, but there are some deliciously savory versions. In this recipe, a mashed potato roll encloses all kinds of things dear to the Spanish palate: anchovies, good canned tuna, red peppers, and olives. The dish is a tad kitschy—the Spanish equivalent of a tuna casserole or vitello tonnato—but so good, it’s impossible not to love. Serve it as a substantial tapa or a l