Dump the shortening, flour, salt, and sugar into a large bowl and work it together with a pastry cutter until you have coarse crumbs.

Pour in the egg, water, and vinegar and stir until just combined.

Separate into 2 balls of dough and place in freezer bags.

Place each bag in the freezer. You'll only need one ball of dough for this pie, the second should keep in the freezer for 6 months or more.

Remove one ball of dough after 20 minutes in the freezer and roll it out on a floured surface into a 10 inch circle.

Place the dough in the pie pan and tuck the edges under to make a neat, thick crust around the edges. Crimp the edges with your fingers or a fork.

Place in the refrigerator until ready to fill.

In a large bowl, beat together the egg, sugar, flour, corn starch, and vanilla until well combined.

Dump in the strawberries and rhubarb and toss to coat in the mixture.

Pour the mixture into the prepared pie shell.

In a medium bowl, cut together the flour, sugar, oats, and butter with a pastry cutter until you have coarse crumbs.

Sprinkle over the top of the pie.

Place the pie in a preheated 400 degree oven for 10 minutes.

Reduce heat to 350 and bake for an additional 25-30 minutes or until the fruit is hot and bubbly and the crust is browned.

Cool on a wire rack.