Heat olive oil and butter in a heavy-bottomed pot.

Add diced onion and sauté until soft (4-5 minutes).

Add rice and stir to coat with oil.

Add water and salt, then cover and cook until water is absorbed.

Stir in corn and cook covered for 5 minutes more, ensuring rice is cooked.

Allow the rice mixture to cool completely.

Combine parsley and parmesan cheese with the cooled rice mixture.

Make rice balls and stuff each with a mozzarella cheese cube.

Ensure the cheese is completely covered with rice.

Arrange flour, beaten eggs, and breadcrumbs in separate bowls.

Coat rice balls in flour, shaking off excess.

Dip the balls in beaten egg.

Roll balls in breadcrumbs until evenly coated.

Repeat for remaining balls.

Heat sunflower oil in a skillet over medium flame.

Add coated rice balls in batches and cook until golden brown.

Serve with marinara sauce or ranch.