3 tablespoons smooth Dijon mustard, plus more for serving
6–7 cups water
1/4 cup baking soda
Coarse sea salt
For the sausages and caramelized onions, set a large sauté pan over medium heat. Add in the oil along with the sausages and, using a wooden spoon, break the sausage up into bite sized pieces. While the sausage cooks, peel, halve, and thinly slice the onions.
Once the sausage is fully cooked and golden brown, use a slotted spoon to remove the sausage from the pan, leaving behind any fat that has rendered out. Add the onions to the pan and allow them to cook, undisturbed, for about six to eight minutes or until they start to colour. Season the onions with salt and pepper, stir in the beer, and turn the heat down to medium-low. Continue cooking the onions, stirring frequently, until they are golden and caramelized, about ten to 15 minutes. When caramelized, remove the onions from the heat.
Preheat your oven to 450ºF and line a rimmed baking sheet with parchment paper. Spray this with non-stick cooking spray and set aside.
Lightly dust a work surface with all-purpose flour and divide the pizza dough into eight equal pieces. Flatten a piece of dough into a thin circle and brush the edge of half of the circle with the egg wash. Place about 1/3 cup of grated cheddar cheese onto one half of the dough followed by some of the sausage and onions. Squeeze a little Dijon on there and fold and shape the calzone into a half-moon shape, being sure to seal, crimp, and pinch the edges closed. Repeat until you have eight calzones then set aside.
In a large pot, combine the water and baking soda and set it over high heat to come to a boil. When the water comes to a boil, set the prepared baking sheet next to stove and have a large slotted spoon handy. Working in batches of two or three, place the calzones in the boiling baking soda water for about 30 to 40 seconds, flipping halfway through. Right now, you’re pretzeling the pizza dough so it’ll get nice and golden brown and chewy when it bakes. Transfer to the prepared baking sheet, being sure to leave at least a few inches between each. Continue until all of the calzones are done.
Brush the top of the calzones with the remaining egg wash and sprinkle with the coarse salt. Bake in the preheated oven for 15 to 17 minutes or until a deep golden brown. Allow the calzones to cool for a few minutes before serving with more mustard and digging in.