Preheat oven to 350°F and prepare a baking sheet.
In a large bowl, cream softened butter and sugar until smooth and well combined.
Add the egg yolk and vanilla extract and mix until incorporated.
Add flour and salt and mix just until a soft dough forms.
Scoop portions of dough and roll into balls.
Roll each dough ball in the shredded coconut until coated.
Place the cookies on the prepared baking sheet.
Use your thumb or the back of a small spoon to make an indentation in the center of each cookie.
Fill each indentation with a small amount of jam or preserves.
Bake at 350°F for 10–12 minutes, or until the cookies are lightly browned.
Allow cookies to cool on the baking sheet for several minutes before transferring them to a cooling rack.
Cool completely before serving or storing.
