In large mixing bowl, beat butter, sugar and vanilla until light and fluffy. Gradually stir in flour until well blended. Stir in macadamia nuts. Place dough on wax paper and shape into a roll two inches in diameter. Wrap in paper and foil and chill at least two hours or overnight. Preheat oven to 300 degrees. Cut roll into slices approx. quarter to 1 cm thick. Bake on ungreased baking sheet for 20 minutes or until cookies begin to brown. Remove from oven; cool on wire rack. Meanwhile, in a small bowl melt chocolate chips (microwave works well) and stir in shortening. Mix well. Dip one end of each cookie into chocolate mixture and place on wax paper. Refrigerate cookies until chocolate hardens. Store in cool place. Makes 2-3 dozen cookies.