In the bowl of an electric mixer, sprinkle the yeast over the warm water. Stir to dissolve. Add the sugar, salt, eggs and evaporated milk. Beat until blended. Add 2 cups of the flour by big spoonfuls. Beat until smooth. Add the shortening, and then beat in the remaining 1 1/2 cups flour. Cover the bowl with plastic wrap and chill in the refrigerator for 3 hours.
In a large electric fryer, preheat the oil to 360 degrees F.
Roll out the dough to a 1/8-inch thickness on a lightly floured work surface. Cut the dough into 2 1/2-inch squares.
In batches of 8, fry the squares in the hot oil until lightly browned on both sides, 2 to 3 minutes. Drain on paper towels. Sprinkle heavily with confectioners' sugar.