In a large mixing bowl, combine the all-purpose flour, instant yeast, sugar, and salt. Gradually stir in warm water until a soft dough forms.

Knead the dough for about 5-7 minutes until smooth and elastic. Place in a greased bowl, cover with a damp cloth, and let rise in a warm area for about 1 hour.

Once risen, punch down the dough. Divide into portions, roll each into a long rope, and twist to form pretzel shapes, tucking mozzarella inside each.

In a large pot, bring about 8 cups of water to a gentle boil. Stir in 1/2 cup of baking soda. Boil each pretzel for 30 seconds before removing to drain.

Preheat oven to 425°F (220°C). Place pretzels on a baking sheet, sprinkle with coarse salt, and bake for 12-15 minutes until golden brown.

Let pretzels cool on a wire rack for a few minutes before serving warm with marinara or garlic butter.