Preheat oven to 375 degrees. Bake pastry shell for 10 minutes; remove from oven. Reduce heat to 325 degrees. In saucepan, over low heat, melt margarine and chocolate chips. In mixer bowl, beat chocolate mixture with Eagle brand, biscuit mix, eggs and vanilla until smooth. Add nuts and pour into pie shell. Bake for 35-40 minutes, until center is set. Serve warm or at room temperature with ice cream. Refrigerate leftovers.