Preheat your oven to 375°F (190°C).
In a skillet, heat a little butter or oil over medium heat. Add the chopped onion and cook until softened, about 5 minutes.
Stir in the minced garlic and cook for another minute. Remove from heat and set aside.
In a large bowl, combine the corn kernels, grated cheese, milk, eggs, and melted butter. Mix well.
Stir in the cooked onion and garlic mixture.
Add the cornmeal, baking powder, salt, black pepper, and dried oregano (if using). Mix until well combined.
Pour the mixture into a greased baking dish or a 9x13-inch pan, spreading it out evenly.
Bake in the preheated oven for 30-40 minutes, or until the top is golden brown and the center is set. A toothpick inserted into the center should come out clean.
Allow the Chipa Guazú to cool slightly before cutting into squares or slices.
Garnish with fresh parsley or cilantro if desired.
Enjoy your meal!