Cream together in medium sized bowl: butter, sugar, egg, vanilla
In a medium bowl sift flour and salt together
With a blender on low slowly add the flour mixture to the butter mixture. Blend until fully combined.
Dish out 1 rounded tsp full at a time. Shape into balls and then coat in granulated sugar.
With the tip of a wooden spoon handle, or gently with your finger, make a small bowl shape at the top of each ball.
Dish strawberry jam into a Ziploc sandwich bag and push down to the botton. Cut a small diagonal tip in a bottom corner of the bag and slowly squeeze into the bowl shape of each cookie. Do not overfill