Mix together the butter, sugar, eggs, and flavorings.
Blend in flour, baking soda and cream of tartar. If the dough is too soft for you to work with it then chill for 1 hour. You don't want to add more flour.
Preheat Oven to 375 Degrees.
Divide the dough into 12 equal pieces on a lightly greased baking sheet and shape them into an oval shape. You want this to be wide and twice as long as wide, or maybe even a little longer. It's going to be a big cookie.
Use a wooden spoon to make a furrow lengthwise down the middle, but not extending all the way to the ends. You don't want the jam to leak out of the furrow.
Now spread some of your favorite jam into the furrow.
Bake approximately 10 minutes. You don't want them to get dark. They will remain very light in color.
Cool on the baking sheet for 2 minutes and then remove to a wire rack.
Once they are cool, drizzle them with the icing. I hope you enjoy them. They should be very soft and very rich.