Preheat oven to 425F.
Bring a stock pot or dutch oven with 3-4 inches of water to a boil.
Unroll the refrigerated pie crust and keep on the paper.
If using a type that needs to be rolled, use a roller to roll out the dough to approximately 1/2 inch thickness.
If using already rolled dough, fold in half so that its about 1/2 inch thick and press down slightly to adhere.
Use a bowl approximately 6 inches across to create two 6-7 inch pizzas (cut around the outside of the bowl with a paring knife). Discard the remaining dough or save for later.
In a small bowl, whisk together one egg with the water.
Brush each pizza dough VERY lightly with the egg wash. If any pooling occurs, pat lightly with a paper towel.
Slowly pour the baking soda into the boiling water (be careful, it will bubble up).
Place the first pizza crust into the boiling water. It will immediately fall to the bottom, so use a wooden spoon to lightly bring it back up to the top (see video).
Let cook in the boiling water for 25 seconds, then use two spatulas to carefully flip. Let cook another 20 seconds and then remove from the water with the spatulas, placing on parchment and set aside.
Repeat with the second pizza crust.
Once on the parchment. Liberally brush each crust with the egg wash once more. Brush all over, but put extra egg around the outside rim. Sprinkle generously all over with sea salt.
Bake in the oven at 425F for 8 minutes.
While the pizza dough initially cooks, make the cheese sauce.
In a medium, heavy-bottom saucepan set over low heat, combine cheese and cornstarch. Toss to combine.
Add evaporated milk and hot sauce and whisk constantly until cheese is melted. Continue whisking about 5 minutes or until the cheese is bubbly and has thickened.
If cheese has thickened too much, add additional evaporated milk.
Once pizza crust has cooked, remove from the oven. Allow to cool for about 5 minutes.
Top each with cheese sauce, leaving about an inch rim around the outside for your pretzel crust. (Use the extra as nacho cheese for dipping, nachos, tacos, or anything!)
Top each pizza with one cup mozzarella cheese, then 10-12 pepperonis.
Bake another 6 minutes or until golden brown and melty/bubbly.
Slice and serve!