Translated from "Atrévete a Cocinar con Karlos Arguiñano". Note: Spring onions are much bigger in size in Spain than in the US. I saw them in an American grocery store once labeled "knobby onions". They're about the size of a small onion, available year-round, and depending on the season they can be either extremely acidic or suitable enough to sprinkle raw on a salad. Though they look young and tender with verdant shoots and glowing white bulbs, they still make my eyes water to chop. You might want to use several (4-6) North American green onions, or just use a an ordinary white onion. Also, only the white part of the spring onion is used. The recipe says just to use "un bote en conserva" of beans (a can or jar cooked), and the jar of beans in my fridge is net weight 570g so that's what I put.