In a bowl, mix the butter, pisco, lime juice, lime zest, aji amarillo, simple syrup, garlic and salt until smooth. Fold in the breadcrumbs last so they stay light and textured. Chill 10–15 minutes to firm slightly.
Heat the broiler to high. Arrange the oysters on a tray packed with rock salt so they stay level.
Spoon about 1 tablespoon of the breadcrumb butter onto each oyster. Broil 4–6 minutes, until the oysters just curl and the topping is bubbling and golden.
Remove from the heat. Add a drop of bitters if using, a sprinkle of fresh cilantro and a final hit of lime zest.
