In a large bowl, combine the flour, yeast, salt, and sugar. Stir in the warm water and melted butter until the dough begins to come together.

Turn the dough out onto a floured surface and knead for about 5-7 minutes, until smooth and elastic. If the dough is too sticky, add more flour, a tablespoon at a time.

Place the dough in a lightly greased bowl, cover with a damp cloth or plastic wrap, and let it rise in a warm spot for about 1 hour, or until doubled in size.

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

In a medium bowl, combine the mozzarella, Parmesan, and chopped rosemary to make the filling.

Once the dough has risen, punch it down and divide it into 8 equal pieces. Roll each piece into a long rope, about 18 inches long.

Place a cube of mozzarella and a small amount of the Parmesan-rosemary mixture in the center of each dough rope. Pinch the edges of the dough around the cheese to seal it.

Shape each stuffed dough rope into a pretzel by twisting the ends and securing them to form a loop.

In a large pot, bring 10 cups of water and ½ cup of baking soda to a boil. Carefully drop each pretzel into the boiling water, one at a time, for about 30 seconds. Use a slotted spoon to remove the pretzels and place them on the prepared baking sheet.

Brush each pretzel with the melted butter and sprinkle with coarse salt.

Bake the pretzels for 12-15 minutes, or until golden brown.

Allow the pretzels to cool slightly before serving.