Preheat oven to 350°F. For crust, in mixer bowl, combine butter, flour, sugar and salt; mix just until crumbly (mixture will be dry). In small bowl, combine egg yolk and vanilla; drizzle over flour mixture and mix by hand until evenly moist and egg is distributed evenly. Form dough into a disc. On a lightly floured surface, roll dough to an 11-in. circle. Transfer dough to pan and press evenly over bottom and up sides of pan, trimming off excess. Prick bottom of crust with fork. Bake 16-18 minutes or until golden brown. Cool completely in pan on cooling grid; carefully remove from pan.