I’d love to be able to tell you that I found the recipe for these crostini in a fifteenth-century Florentine manuscript written backward, but the truth is that the history of the dish begins in my own kitchen. I had got carried away slicing onion and made a lot more than I needed for something I was cooking. I cooked it all anyway, and to the surplus I added some diced tomato and chili pepper, processed it to a creamy consistency, mixed in some basil, and I had onion spread.
The trick in cooking thin-sliced onion like this is to cook it very slowly with salt in a covered pan. The salt causes the onion to release liquid, which in turn steams the onion, making it very soft. Stir from time to time, and eventually all the liquid will evaporate. When that happens, remove the lid from the pan and stir the onion until it becomes colored a very light nut brown. It may take between 25 and 30 minutes. This is a useful technique because you can use it in many dishes, including a pasta sauce made solely with onions.
Spread over rounds of crusty bread, which need not be toasted or grilled if one enjoys a tender consistency. The spread can be prepared hours in advance, but it tastes better at room temperature, or even still lukewarm, rather than refrigerated.
© 1997 Marcella Hazan estate. All rights reserved.