Heat a medium pot or dutch oven over medium-high heat. Add the olive oil and onion and cook for about 2 minutes, stirring occasionally until the onion is translucent.
Add the garlic and stir for about 30 seconds until very fragrant. Add the rice and toast for 3 minutes, until the rice starts to get a few brown toasty spots.
Lower the heat to medium and add the tomato paste, chipotle pepper, smoked paprika, chili powder, a pinch of salt and ½ cup of chicken broth. Stir to dissolve the tomato paste and continue stirring constantly until all the liquid is absorbed by the rice.
Continue adding broth ½ cup at a time, stirring constantly, until it is nearly absorbed before adding more. Continue tasting with each step and add more salt if necessary.
The risotto rice is done when the rice is tender and the liquid is creamy, about 15 minutes. If you've used all the broth and the rice still isn't fully cooked, continue cooking by adding ½ cup of broth until tender.
Remove from heat and stir in cilantro. Taste and season with more salt if necessary. Transfer the risotto rice to a bowl, cover and let cool completely in the refrigerator (about 2 hours) or the freezer (about 1 hour).
Preheat oven to 350ºF. Line a baking sheet with parchment paper. Crack eggs into a small bowl and lightly beat with a fork. Place panko breadcrumbs in a medium bowl and set aside.
In a medium mixing bowl, add the cold risotto rice, Parmesan cheese and plain breadcrumbs. Mix together with a spoon or fork until fully combined.
Using an ice cream scoop, scoop out the cold rice mixture (about 2 heaping tablespoons worth) and form into a ball.
Make a small indent in the middle of the ball with your thumb and place 1 cube of mozzarella in the middle. Pinch the rice ball closed around the mozzarella and form into a ball again.
Roll the ball in the beaten eggs, shake off any excess and then place in the panko breadcrumbs. Roll the ball in the panko breadcrumbs and then transfer to the lined baking sheet. Repeat the process with the remaining risotto rice and mozzarella until you have about 16 arancini rice balls.
Spray the rice balls with cooking or olive oil spray and bake for 30 min.
Garnish with chopped cilantro and grated Parmesan cheese. Serve with your favorite marinara sauce and enjoy!