Beat egg lightly in bowl. Add sour cream, sugar, vanilla, flour and optional nutmeg to beaten egg. Blend until smooth. Peel, core and slice pears thinly. Add pear slices to custard in the bowl. Toss pear slices in the custard until all pear slices are coated with custard. Place the coated slices in pie dish with the uncooked pie crust. Arrange the coated sliced pears in the crust to be more or less flat. Mix all topping ingredients, except the nuts (if used), together. Sprinkle the nuts evenly over the top of the pie. Pour all of topping on top of pie and smooth out the topping. Bake at 375 F. (glass pie dish) for 1 hour and 10 minutes.
