Named for the curved shape of its blade, a mezzaluna ("half moon" in Italian) can look strange the first time you see one, Tina1981 notes on Chowhound. A traditional mezzaluna is designed to be used with two hands: It has two handles and one or two blades. Obviously, it's not for every cutting task in the kitchen.
Chemicalkinetics thinks a chef's knife works better for chopping most things, but a mezzaluna is useful when you need to chop a large amount of herbs (it's easier on the hands). Novelli uses a mezzaluna to make finely minced fillings for pasta, meat roulades, and pastry: It yields "a nice consistency so you can actually taste the individual ingredients." Mezzalunas are best used with a shallow wooden bowl or a cutting board with a concave depression. Otherwise, your herbs will fly all over the place, Manassas64 says.
Speaking of curved knives, the single-blade ulu is traditional in Alaska. Unlike a mezzaluna, it's designed for one-hand chopping (eperdu uses it for nuts and herbs). Pizza-lovers take note, KSlink says: It also does a killer job rendering a medium pepperoni pizza into slices.
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