Mazapan in Mexico is not the same as the same as the bright yellow marzipan paste used in cake decorating that you are probably already familiar with. It a slightly crumbly, very very sweet puck of nuts and sugar.
Peanuts are normally used but any nut will do fine.
The procedure is simple, nuts and sugar are combined in the food processor and chopped until the oil from the nuts is released (a couple of minutes) and a loose cake can be formed. For two cups if nuts use about a cup and a half of powdered sugar. I don't keep powdered sugar on hand so I use granulated sugar but process it separately first to make it finer. The texture is much looser than European marzipan. There is no way you could make those miniature models of fruit from the Mexican version.
Marzipan is very common here, you can see it at most shop checkouts and it's most commonly sold in packs of four two inch pucks, though you do also see larger cakes of it too.
It's simple and tasty, and ideal treat to make with kids. But be warned, when I say it's very, very sweet - I'm not joking.