Preheat the oven to 350 degrees F (175 degrees C).
In a medium bowl, stir together 3/4 cup sugar, 1 tablespoon flour, cinnamon and salt. Mix in the egg and sour cream until smooth. Add pears, and stir gently until coated. Pour the mixture into a graham cracker crust.
Bake for 25 minutes in the preheated oven. While the pie is baking, make the topping in a medium bowl. Stir together the sugar and flour. Cut in butter until the mixture resembles coarse crumbs. Sprinkle topping over the pie.
Bake for an additional 30 minutes. Cool completely before serving.