Cream together butter and sugar. Mix beaten eggs, vanilla and milk in a small bowl. In a medium bowl, sift together flour, salt and baking powder. Alternate adding dry mixture and egg mixture to creamed butter and sugar until blended. Allow to chill, at least three hours or so, if not even overnight.
To prepare filling, mix together all ingredients until smooth.
To form cookies, scoop rounded tablespoons of dough and roll into a ball. Press ball flat into a circle between 1/8 and 1/4 inch thick, the circle should be about 2 1/2 inches in diameter. Place a 1/2 tsp filling in center of dough. With fingers, lift up dough all around edge and seal together above filling. Making sure there are no leaks, place seal side down onto an ungreased cookie sheet and press down lightly.
Bake 15-20 minutes in a 375 degree oven. Allow to cool on sheet for 1 minute, then place on cooling racks. For a spectacular holiday presentation, heat chocolate chips and milk and stir until blended. Using a fork drizzle over cookies and sprinkle with crushed candy canes.