* One 10-oz package of Nestle Toll House Mint-Chocolate Morsels; divided. ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Melt, over hot (not boiling) water, half cup mint-chocolate chips, stir until smooth. Cool to room temperature, set aside. In a large bowl, combine butter and sugar; beat until creamy. Add egg and vanilla extract, blend well. Gradually beat in flour and salt. Place 1 cup of dough in a small bowl. Add melted chips; blend thoroughly. Shape into a ball, flatten, (mixture will appear curdled). Cover with plastic wrap. Shape remaining dough into ball; flatten. Cover with plastic wrap. Chill until firm, about 1.5 hours). Preheat oven to 190ºC . Between sheets of waxed paper, roll each ball of dough into a 13 x 23 cm rectangle. Remove top layers of waxed paper and invert the chocolate dough onto the plain dough. Peel off waxed paper. Starting from the long side, roll up jelly roll stype. Cut into 1 cm slices; place on ungreased cookie sheet. Bake at 190ºC . for 7 to 8 minutes. Cool completely on wire racks. Melt over hot, (not boiling), water remaining 1 cup of chips; stir until smooth. Spread flat side of cookie with half slightly rounded teaspoonful melted chocolate. Chill until set.