A good tea cookie. Watch carefully during baking to prevent burning.
Cream shortening and brown sugar; stir in eggs and vanilla, and beat well. Combine flour, cream of tartar, and baking soda, and add to egg mixture. Chill dough for 45 minutes. Roll dough into a long strip 5 inches wide and spread with the filling (below). Roll up dough lengthwise (like a jelly roll) and cut crosswise into 3 sections. Wrap each section in waxed paper and chill for several hours, or freeze. To bake, cut cookies into ⅜-inch slices, and bake at 375 degrees F for 8 to 10 minutes.
Combine all ingredients and cook until mixture thickens, about 5 to 8 minutes. Cool, spread on cookie dough, and proceed as directed.