Source: Frida's Fiestas: Recipes and Reminiscences of Life with Frida Kahlo written by Diego Rivera's daughter Guadelupe Rivera and Marie-Pierre Colle

16 limes
1 tablespoon baking soda
3 cups granulated sugar
3 cups water

Cocada
1 cup granulated sugar
1 cup water
1 coconut, peeled and finely grated

In a non-reactive saucepan, simmer the limes in water to cover until slightly softened. Pour the contents of the saucepan into a clay pot. Sprinkle with the baking soda, cover, and let stand overnight.

The next day, drain the limes. Cut a small slice from the tops and carefully hollow them out. Discard the pulp and return the limes to the clay pot with enough hot water to cover. Cover with a dish towel and a tight-fitting lid. Let stand overnight.

The next day, drain the water and replace it with fresh hot water. Let stand, covered, as above. Repeat this process for 3 or 4 days, until the limes are no longer bitter.

Combine the sugar and water in a copper pot. Bring to a boil and add the limes. Simmer until the syrup is quite thick. This takes about 45 minutes to 1 hour. Let cool overnight.

To serve, remove the limes from the syrup and fill with Cocada.

To make the Cocada, combine the sugar and water in a saucepan and bring to a boil. Stir in the coconut and cook, stirring constantly, until thick. Let it cool completely.