In a mixer with whisk attachment, beat the egg whites until frothy. Add cream of tartar and beat until soft peak forms. Add sugar gradually, and continue beating until stiff, but not dry. Fold in vanilla extract.
Put ample amount of meringue in a piping bag with a star tip. Pipe meringue mixture on the sides of the prepared paper cupcake cups, leaving a hole at the center.
Bake for 30 to 35 minutes or until set.
In a double boiler, combine all the ingredients for the filling, and cook until thick. Let it cool.
Dust powdered sugar on top of the brazo cups, then put ample amount of the filling on a piping bag and pipe filling at the center of the brazo cups. Serve.