A delicate little cookie filled with jam in the middle!
Mix butter and sugar together until blended well, about 2 minutes on medium in mixing bowl. Mix in salt and flour, just until all ingredients are incorporated. Do not over mix.
Add a small amount of water (if needed) to form a soft dough that can be shaped. Shape the dough into a large disk in the mixing bowl. Cover with plastic wrap tightly and refrigerate for about 1-2 hours until thoroughly chilled.
Preheat oven to 350 degrees.
Shape the dough into 1/2-1 inch balls. Dip one side of the dough into sugar. Place the balls two inches apart on a cookie sheet, with the sugar-dipped side facing up.
Bake on middle rack for about 8-10 minutes, or until cookies are firm to the touch.
Remove cookies from oven and let cool completely. Fill with jam.
Yields about 2-3 dozen cookies, depending on size of dough ball.