My Puerto Rican grandmother stockpiled plantains in the pantry of our New York City apartment like preserves in a root cellar. While they were green and as starchy as potatoes, she’d double‑fry them for tostones or pound them into a mash with flavorful fats. As they transitioned to yellow, softening slightly and taking on a touch of sweetness, she’d grate them into soups or turn them into dumplings. But for me, the real prize came days or even weeks later, when their skins were mostly black and their flesh creamy and sweet: She’d fry up a batch of plátanos maduros fritos (fried ripe plantains) to make the meaty casserole called pastelón. Then she’d layer the caramelized slices with a swath of picadillo—ground beef simmered in sofrito and tomato sauce and studded with olives, capers, and pimentos—drizzle beaten egg over the top, and bake the casserole in the oven, where its flavors would meld.