Cream butter, sugar, and vanilla until blended. On low speed, beat in flour. Stir in half chips. Cover and chill till firm (though not too firm, I had to let mine sit til it was workable!). Shape heaping TBs into 8 cm-long, 1 cm-thick logs (like biscotti). Place on lightly greased cookie sheet and bake in a 350 degree oven for 8 minutes or until golden brown. Cool. Melt remaining chips and oil, dip 2 cm of one end of each cookie into chocolate. Makes 36.