Heat oven to 375°F Partially bake crust 5 to 7 minutes.
Meanwhile, in large bowl, beat butter and brown sugar on medium speed until light and fluffy. Beat in eggs, one at a time, beating well after each addition. Add melted chocolate, dry coffee and vanilla; mix well. Stir in flour and walnuts.
Pour mixture into partially baked crust. Bake 25 to 30 minutes or until set. Serve warm with whipped cream or ice cream, if desired.