Preheat the oven to 350 degrees Fahrenheit. Cut the guava paste into squares that are

about ¾ inch thick and 2 and ½ inches wide. Set them aside. In a large bowl cream together the butter and sugar.

Add the egg yolk and vanilla extract and mix until well blended. Add the flour, ½ cup at a time, mixing well between additions, until a relatively coarse dough forms.

Place some of the dough in the palm of one of your hands and flatten it. Place a slice of guava paste on top of the dough and then grab another handful of dough and compress it on top of the guava paste.

Flip the cookie back and forth between your palms, compressing the crumbly dough

until the slice of guava paste is completely encased in the dough and the dough

crumbs have solidified enough to form a relatively smooth dough casing.

Place the cookie on an ungreased cookie sheet and repeat this process until all of the dough or guava slices are used. Bake for 25 minutes, then remove the pan from the oven and allow to cool for 20 minutes before serving.