In a medium mixing bowl, whisk together the cornmeal, salt, and queso fresco until evenly combined.

In a saucepan, heat the water, milk, and butter over medium heat until steaming. Pour this into the cornmeal blend and stir well. Cover and let it sit for 5 minutes to thicken.

Preheat your griddle over medium-low heat. Take about ⅓ cup of dough, roll it into a ball, and gently flatten it to form a 5-inch patty. Add shredded mozzarella to the center, fold it over, and reshape it into a ball again. Flatten it back into a 5-inch disc, sealing the cheese inside.

Place the formed patties onto the preheated griddle. Cook each side for about 4 minutes or until golden brown. Adjust the heat as necessary.

Allow the arepas to cool for about 3 minutes before serving. Enjoy them plain or with avocado, pico de gallo, or sour cream.