In a large mixing bowl, combine warm water, yeast, and sugar. Let it sit for about 5 minutes until it becomes frothy.

Once frothy, mix in the melted butter and salt. Gradually add the flour, one cup at a time, mixing until a dough begins to form.

Knead the dough on a floured surface for about 5-7 minutes until the dough is smooth and elastic.

Place the dough in a greased bowl, cover it with a clean towel, and let it rise in a warm place for approximately 1 hour, or until it doubles in size.

Preheat your oven to 425°F (220°C) and line two baking sheets with parchment paper.

In a large pot, bring the 10 cups of water and baking soda to a boil.

Punch down the risen dough and divide it into 12 equal pieces. Roll each piece into a long rope, about 20 inches long. Form each rope into a U shape, twist the ends together, and fold back down to form a pretzel shape.

Carefully place each pretzel into the boiling baking soda bath for about 30 seconds. Use a slotted spoon to remove them and transfer them to the prepared baking sheets.

Cut small slits in the tops of the pretzels and place a cube of mozzarella into each slit.

Brush the pretzels with the beaten egg and sprinkle with coarse sea salt.

Bake for 12-15 minutes or until they turn golden brown.

Allow to cool slightly before enjoying.