Preheat oven to 325 degrees.

In a bowl cream together butter and sugar. Add beaten egg yolk and stir well to combine.

Sift flour and salt into mixture. Mix well.

Roll into balls the size of walnuts.

Roll balls in slightly beaten egg white and then in chopped nuts or toasted coconut. Place on a parchment lined baking sheet.

Press thumb in each cookie to form a well.

Bake for 5 minutes. Take cookies out and press cookies with thumb again. Return to oven and cook for 10 more minutes.

Remove from oven. If you like turn a chocolate wafer upside down and gently press into each cookie. The warmth of the cookie will melt the chocolate a little. Top with your favourite jam or jelly while still warm.