Preheat oven to 400°F. Line a 9-inch pie plate with piecrust. Trim crust to 1/2 inch beyond edge of pie plate. Fold under extra crust and crimp edge. Line crust with foil and fill with dried beans.
Bake for 15 minutes, or until light brown. Cool crust for 5 minutes; discard foil and beans. Lower oven temperature to 350°F.
Meanwhile, in a large bowl, using a rotary beater or fork, beat the egg whites and egg just until mixed. Whisk in the maple syrup or organic syrup, brown sugar, flour, butter, and vanilla just until smooth. Stir in the walnuts.
Pour the syrup mixture into baked crust.
Bake for 40 to 45 minutes, or until a knife inserted in the center comes out clean. Cool for 1 hour. If not serving immediately, cover and store in the refrigerator.