Preheat the oven to 425°F.  Line a baking sheet with parchment paper

Make the risotto balls. Mix the risotto and egg in a medium mixing bowl.  Using an ice cream scoop or large dough scoop, form the risotto into a ball. While the risotto is still in the scoop carefully push a mozzarella cube into the middle of the ball. Remove the ball from the scoop and place on the lined baking sheet. Repeat until you have formed 12 balls.

Chill. Place the baking sheet in the refrigerator and chill for 15 -30 minutes.  

Coat the arancini. While the arancini are chilling mix the panko, basil and olive oil in a shallow dish. Remove the arancini from the refrigerator and carefully roll each ball in the panko mix, being sure to coat all sides. Return to the baking sheet. Repeat until all of the risotto balls are coated.

Bake. Spray the arancini with olive oil spray, coating well. Bake 10-15 minutes until arancini are golden brown.  Remove from oven and serve immediately.