In a large mixing bowl, combine warm water, instant yeast, and sugar. Allow to foam for about 5 minutes.

In a separate bowl, whisk together all-purpose flour and salt. Gradually mix flour with yeast mixture to form a dough, then knead for 5 minutes using a stand mixer or 8 minutes by hand until smooth.

Once dough is ready, fold in chopped rosemary and grated Parmesan, shape into a ball, place in a greased bowl, cover, and let rise for 1 hour.

Preheat oven to 425°F (220°C). Punch down the dough and divide into eight pieces. Flatten each piece, place a cube of mozzarella inside, seal, and twist into pretzel shape.

In a pot, bring water to a boil and add baking soda. Gently lower each pretzel into boiling water for 30 seconds on each side, then let drain briefly.

Place boiled pretzels on a parchment-lined baking sheet. Brush with melted butter and sprinkle with coarse sea salt. Bake for 12-15 minutes until golden.