2 tablespoons brown sugar
1 cup warm whole milk
3 cups flour
1 packet yeast
1/2 cup finely chopped deli ham
1/2 cup shredded mozzarella cheese
4 teaspoons baking soda
4 tablespoons unsalted butter, melted
1 tablespoon kosher salt
Turn dough out onto a lightly floured surface. Divide into 4 equal pieces. Lightly dust hands and rolling pin with flour. Roll out one of the sections into a 12-by-4-inch rectangle. With the long side facing you, gently press 1/4 of the ham and cheese into the bottom third of the dough, and roll as tightly as possible, starting at the end that has the filling. Cut into twelve 1-inch pieces and transfer to a parchment-lined baking sheet. Repeat with remaining 3 portions of dough.
Let rest, uncovered, at room temperature for 30 minutes. Meanwhile, preheat the oven to 400 degrees. Bring 6 cups of water to a boil. Add the baking soda and reduce heat to a gentle simmer. Boil pretzels in batches, cooking about 20 seconds each, turning once. They should be slightly puffed. Use a slotted spoon to transfer them back to the baking sheet. Bake until puffed and golden-brown, about 15 minutes. Brush warm pretzels with melted butter and sprinkle with coarse salt.