Prepare the majarblanco by placing the closed can of condensed milk inside a pot with boiling water and letting it cook for approximately two hours. This will leave the ingredients thick and brown.
Sift flour, corn flour and baking powder together. Beat the softened butter with the powdered sugar until it has a creamy texture. Add the egg yolks one by one, whipping each completely into the mixture. Slowly add the flour mixture and the grated lemon skin, continuing to whip the mixture as you do. Make a ball of this dough and let it rest for 20 minutes on an open table.
Preheat the oven to 350 degrees F. Scatter some flour on a flat surface and using a rolling pin work on the dough until it is a bit less than half an inch thick. Then cut circles of about 2 inches in diameter. Bake the circles until they are not quite brown. Let them cool down completely.
Then make little sandwiches using the manjarbanco between two of the cookies. Seal the edges with manjarbanco and then roll each of them edgewise through some shredded coconut.