Cream the softened butter and sugar in a mixing bowl until smooth and creamy, about 2-3 minutes.

Incorporate the egg yolks into the butter-sugar mixture and mix until thick and pale yellow.

Sift together the self-rising flour and cornstarch, then gradually mix into the wet ingredients to form a dough.

Knead the dough gently into a smooth ball, wrap in plastic wrap, and refrigerate for about 10 minutes.

Roll out the chilled dough to about ½ inch thickness, then cut into 3-inch circles.

Place cookie circles on a parchment-lined baking sheet and prick each lightly with a fork.

Bake in a preheated oven at 350°F (175°C) for 20 minutes or until lightly golden around the edges.

Cool the cookies on a wire rack for 30 minutes before spreading with manjar blanco and topping with another cookie.

Dust the assembled cookies with powdered sugar before serving.