Forget the pulverized versions in a supermarket canister—perfect crumbs are not uniform in size. To get truly crunchy toppings or crisp crusts, you need a mixture of line, medium, and coarse crumbs. Making them at home is best, and it’s as easy as pulsing day-old bread in a food processor. The bread shouldn’t be either too dry or too fresh and moist. Just leave leftover bread on the counter overnight, then which into crumbs the next day. Keep the crumbs in a zip-top bag in the freezer and pull out as needed. Make whenever leftover bread is on hand, and you’ll always have a steady supply.