2Sift together flour and cornstarch; set aside. Cream butter until smooth, then add white sugar, confectioner's sugar, vanilla, and salt; beat until fluffy. Slowly add flour mixture to butter mixture, beating on low until dough forms.
3On a floured surface, knead in 1/2 cup chocolate chips. Shape dough into two equal parts, pat each into a 6 inch round, and transfer to baking sheet. Cut into wedges.
4Bake 25 minutes. Remove immediately to cool on wire rack. Melt remaining chips and drizzle over wedges.