Position knife blade in food processor bowl; add pecan pieces and process until pecans are coarsely chopped. Add flour.
Drop 1/2 cup butter, 1 tablespoon at a time, through food chute with processor running; process until mixture is crumbly. Pour orange juice through food chute; process 1 minute or until dough forms a ball. Remove dough; cover and chill 1 to 2 hours.
Roll dough to a 12" circle between 2 sheets of wax paper. Remove top piece of wax paper and invert dough into a 9" pieplate; remove remaining wax paper. Trim edges of crust; prick bottom and sides of dough with a fork. Bake at 350° for 20 to 25 minutes or until lightly browned. Let cool.
Combine chocolate morsels and next 3 ingredients in a small saucepan. Cook over low heat until chocolate and butter melt, stirring often. Remove from heat; stir in vanilla. Spoon chocolate mixture into prepared crust.
Sprinkle gelatin over 1/2 cup chocolate milk in a saucepan; let stand 1 minute. Stir in remaining 3/4 cup chocolate milk, 1/3 cup sugar, and coffee granules. Cook over low heat 2 minutes, stirring until gelatin and coffee granules dissolve.
Gradually stir about 1/4 of hot mixture into egg yolks; add to remaining hot mixture, stirring constantly. Cook 1 minute or until mixture reaches 160° (do not boil). Remove from heat; chill 30 minutes or until consistency of unbeaten egg white.
Fold 2 cups whipped topping into gelatin mixture; spoon into crust over chocolate layer. Cover and chill until firm. Garnish, if desired.