To make the crust, dump the shortening, flour, salt, and sugar into a large bowl and work it together with a pastry cutter until you have coarse crumbs. Alternately, combine this in a food processor fitted with the dough blade.

Pour in the egg, water, and vinegar and stir until just combined. If using a food processor, pulse until just combined, being careful not to overmix.

Seperate into 2 balls of dough and place in ziploc bags. Flatten into round discs. Refrigerate for 30 minutes.

Roll one disc of dough out on a floured surface to fit a 9 inch deep dish pie plate. Store remaining disc of dough in the freezer for another use.

To make the filling, whisk together the brown sugar and flour in a small saucepan.

Turn heat to medium and whisk in the evaporated milk, butter, cinnamon, and salt. Continue cooking, whisking constantly, until the butter has melted and the mixture is fully combined and begins to boil.

Continue whisking and let come to a full boil for one minute. Mixture should begin to thicken to the consistency of a gravy.

Remove from heat and stir in the vanilla.

Pour mixture into prepared pie crust and bake at 400 degrees for 5 minutes.

Reduce oven temperature to 350 degrees and continue baking for 25 minutes.

Cool on the counter for at least 2 hours before cutting and serving.