To make crust: In large bowl, combine 3 cups flour, 1 teaspoon salt and 2 teaspoons sugar. Using a pastry blender, cut in shortening until the mixture is crumbly or crumbs are the size of a pea. In a 2-cup glass measuring cup (or bowl), beat egg, vinegar and 5 tablespoons cold water. Slowly add to flour mixture, tossing and stirring with a fork until liquid is absorbed, being careful not to overmix (adding additional 1 tablespoon cold water, if needed). Divide dough in thirds and form each into a disk. Freeze or refrigerate one for later use. Roll out 1 portion on lightly floured surface into a circle large enough to fill a 9-inch pie plate (stoneware or glass is preferred) with an 1/4-inch overhang (so about 12 inches). Press into plate, leaving extra crust around the edges.
To make filling: In medium bowl, mix 1 cup sugar, 1/3 cup flour, vanilla, cinnamon and dash of salt; set aside. In large bowl, combine blueberries, rhubarb and strawberries. Add the sugar mixture to the berries and gently toss to combine. Place in prepared bottom crust. Add pats of butter on top.
Roll out second pie crust (on lightly floured surface) into a circle large enough to fit as a top crust with overhang (about 11 inches) and place on top of filling. Tuck top edges under bottom crust edges and crimp. Slice air vents on top. Sprinkle sugar on top. Bake at 350 degrees for 1 hour, or until bubbling. Keep an eye on pie and cover edges if needed to prevent overbrowning. Let pie completely cool before slicing and serving.
Nutrition information per serving: