In a large pot, heat 5 tablespoons of olive oil over medium heat.

Add the chopped onion and cook, stirring constantly, until golden brown (about 5-7 minutes).

Add the chicken stock and 7 tablespoons of butter to the pot.

Add the rice, stir quickly, then cover with the lid. Cook the rice until the liquid is absorbed, stirring occasionally.

Once the rice is cooked, stir in the remaining tablespoon of butter.

Spread the hot rice onto a chilled tray and top with shredded Pecorino Romano.

Let the rice cool for at least an hour.

In a pan, heat 2 tablespoons of olive oil over medium heat.

Add the diced celery, carrot, and shallots. Sauté until soft (about 5 minutes).

Add the minced garlic and cook for 1 minute, until fragrant.

Add the ground beef and cook until fully browned, breaking it up with a spoon (about 10 minutes).

Stir in the crushed tomatoes and baking soda. Season with salt and pepper.

Add the frozen peas and bring to a boil, then lower the heat and simmer for 30 minutes.

Drain the meat mixture using a colander, reserving the liquid for dipping sauce.

Take a handful of chilled rice and form a pocket in your palm. Add a generous amount of the meat mixture and a piece of diced mozzarella in the center.

Add another scoop of rice on top and form into a ball, pressing to remove excess moisture.

Place the formed rice balls on a baking tray lined with parchment paper.

Dip each rice ball into the scrambled eggs, then roll in breadcrumbs until well coated.

Heat oil in a pot to 360°F. Fry a few rice balls at a time for about 5-7 minutes, until golden brown and the cheese inside has melted.

Repeat until all rice balls are cooked.

Serve the arancini with the reserved tomato sauce.