This recipe is from the Jewish community of Volos, Greece. Traditionally associated with the Arabs in conquered Spain, marzipan can be found in all Mediterranean cuisines as well as many Arab ones as well. This recipe requires several days to make.
Put the lemon peels in a bowl with water to cover. Let soak for 2 days, changing the water every 3 to 4 hours thru the day and evening.
On the third day, rinse the peels and put into a large saucepan with water to cover. Place over low heat and simmer for 45 to 60 minutes, until peels are very soft.
Remove from the heat and mash to a pulp or pulse in a food processor. You should have about one cup of pulp.
Return pulp to large saucepan and add the ground almonds and 2 cups granulated sugar. Mix well and place over low heat. Stir often with a wooden spoon. Cook until the mixture thickens and starts peeling away from the pan sides.
Remove from the heat and pour onto a chilled marble slab or chilled platter. Let cool.
When cool, spread the powdered sugar onto a separate plate. Kneed the mixture a little and them pinch off pieces the size of hazelnuts. Roll them into balls and then roll in the powdered sugar.
Put onto a large platter and when finished making balls, dust the marzipan again with the powdered sugar.
Let the marzipan rest for 24 hours before serving.