Preheat oven to 350 degrees and grease a 9x13 baking pan.
In a bowl, combine the flour and powdered sugar. Cut in the butter using a pastry blender or two knives until the mixture is crumbly. Sprinkle in water and mix. Press into prepared pan and bake for 17 minutes.
In a medium bowl, combine the egg, sweetened condensed milk, pumpkin, pumpkin pie spice and vanilla and mix well. Fold in the toffee bits and pecans. Spoon over crust when it's done baking.
Bake again for 25-30 minutes or until golden brown.
Chill completely before cutting.