In a mixing bowl, combine warm water (110°F), instant yeast, and sugar, allowing it to foam for about 5 minutes. Once bubbly, add in all-purpose flour and salt, mixing until a dough forms. Knead the dough on a floured surface or with a stand mixer for about 5 minutes until smooth and elastic.

Incorporate chopped rosemary and grated Parmesan cheese into the kneaded dough, ensuring an even distribution. Shape the dough into a ball and place it in a greased bowl, covering it with a towel. Let it rise in a warm area for about 1 hour, or until doubled in size.

Once risen, punch down the dough gently to release the air. Divide it into 8 equal pieces, taking each piece and flattening it slightly. Place a cube of mozzarella in the center, seal well, and roll the dough into 24-inch ropes. Twist and shape each rope into a pretzel form.

Bring a large pot of water to a boil and add baking soda. Carefully place the pretzels in batches into the boiling water, cooking each for about 30 seconds. Use a slotted spoon to drain the pretzels and transfer them onto a parchment-lined baking sheet.

Preheat your oven to 425°F. Brush each boiled pretzel with melted butter and sprinkle with salt. Bake for 12-15 minutes until they turn a beautiful golden brown.