You can make and freeze crust ahead of time; thaw in fridge overnight before preparing the filling.
Prepare Crust: Preheat oven to 400°. Beat first 3 ingredients at medium speed with a heavy-duty electric stand mixer until creamy. Gradually add flour and salt, beating at low speed just until blended after each addition. Add finely chopped pecans, and beat just until blended. Shape dough into a disk, and wrap with plastic wrap. Chill 1 hour.
Place dough disk on a lightly floured surface, and roll into a 13- x 9-inch rectangle. Gently place dough in a lightly greased (with cooking spray) 12- x 8-inch rectangular tart pan with removable bottom. Press dough into pan and up sides; trim off excess dough along edges.
Bake at 400° for 14 to 17 minutes or until lightly browned. Remove pan to a wire rack, and cool completely (about 30 minutes).
Meanwhile, prepare Mousse: Microwave chocolate morsels and 1/2 cup cream in a medium-size microwave-safe glass bowl at HIGH 1 1/2 minutes or until melted, stirring every 30 seconds. Stir in bourbon and vanilla; let stand 5 minutes.
Beat remaining 2 cups cream at medium-high speed with an electric mixer 2 to 3 minutes or until medium peaks form; fold cream into chocolate mixture. Spread in cooled tart shell. Top with coarsely chopped pecans. Chill 4 to 24 hours.
To make in a 9-inch round deep-dish tart pan, prepare crust as directed, and roll into a 12-inch circle; increase baking time for crust to 22 to 27 minutes.