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. Cool on cooling rack 1 1/2 hours. Serve warm with whipped cream or ice cream, if desired.