Mix butter, flour and sugar. Blend with a fork or a pastry blender.
Finish kneading with hands until a uniform dough is obtained.
Roll dough on a flour surface. Cut circles with a round cookie cutter (the size and form are optional).
Transfer them carefully to greased cookie sheet.
Bake in preheated oven 350° F (175° C) for 12 to 15 minutes. Remove from oven. Cool.
To assemble: take one of the cookies, and carefully spread with manjarblanco. Cover with another cookie. Sprinkle with sifted confectioners sugar.
If making a large one, double the recipe, and make 10-inch circles (25 cm). It is better to roll the dough on top of a plastic film or parchment paper. This way it will be easier to transport. Once on the cookie sheet, remove film or paper. Yields: 3 circles.
Proceed as with the small alfajores.