Sift flour and salt. Blend butter, sugar, vanilla. Add flour mixture, milk, 1/4 cup chopped chips. Form in 1" balls. Make thumbprint in center. Bake at 357 degrees for 10-12 minutes. Roll in confectioners' sugar while warm. Cool. For filling, melt 3/4 cups chocolate chips and shortening in a double boiler. Stir ingredients and stir until smooth. Let cool 5 minutes. Fill cookies. Annie's notes: as kids, these were by far my brother's and my favorite cookies at Christmas time (well, besides cut-outs). I still make a double batch for Christmas here; although my brother is 44, he still loves his cookies! Me, too, of course! ----