Wash the sweet potatoes. Remove the potato skin with a peeler. Place each whole potato into the pie dish. Peel enough potatoes to cover the bottom of the dish. Cut long potatoes in half if necessary to fit them. The dish should be filled with potatoes.
Once you have enough peeled potatoes, move them to a large stock pan and cover with water. Prop a lid on the pan and boil for 5 minutes.
Dry the pie dish if necessary. Grease it. Take out 1 pie crust and roll it bigger than the 10-inch dish. Then place it in the dish, letting any extra crust hang over the sides.
Whisk the egg white and water until foamy. Use a pastry brush to brush the egg mixture onto the bottom and sides of the pie crust. Place the crust into the refrigerator for 15 minutes.
Remove the boiled potatoes from the heat, drain, and rinse in cold water.
Preheat the oven to 400°F.
Place each potato on an extra-large spoon and cut 1/4-inch slices. Stop cutting when the knife hits the sides of the spoon so that you don't cut all the way through. Slide the potatoes off the spoon into the chilled crust, being careful not to break them apart. Arrange them so that they fill the crust.
Mix the sugar, cinnamon, flour, and salt and sprinkle the mixture evenly over the potatoes.
In a large measuring cup, add the half and half and vanilla. Stir. Then, pour it over the potatoes, washing some of the sugar from the tops.
Roll the second pie crust bigger than the pie. Use a small plate (or round parchment template approximately 6-7 inches in diameter) and a knife to cut out a hole in the middle. Place the dough on the pie (centering the hole in the middle) and trim any pastry overhang from the bottom and top crusts. Press to seal the seams. Brush the top crust ring with egg white. Then, completely cover the ring with almond slivers. Brush egg white on the almonds using a tapping motion with the brush so as not to disturb the almonds.
Cut the butter into pieces and place on the potatoes in the center opening of the pie.
Make a baking shield for the crust from aluminum foil (leaving the center potatoes uncovered) and loosely place it on top. Bake for 50 minutes. Then, remove the baking shield and bake for an additional 10 minutes.