Sauté the onion and garlic: Warm the olive oil in a large, heavy-bottomed saucepan over medium heat. When the oil begins to shimmer, add the finely chopped onion and crushed garlic. Cook for about 5 minutes, stirring often, until the vegetables soften and release their aroma.

Cook the rice: Add the Arborio rice to the saucepan and stir to coat each grain in the oil, cooking until the rice appears slightly translucent, about 1 minute. Add the salt, pepper, parsley, chicken stock, tomato paste, and butter. Stir well to dissolve the tomato paste and distribute the seasonings. Bring the mixture to a gentle boil, reduce the heat to low, cover, and simmer for 20 to 25 minutes until the rice is tender and the liquid has been absorbed.

Set up a breading station: While the rice cooks, prepare three medium bowls. In the first bowl, combine the flour, salt, and pepper. Beat the eggs in the second bowl until smooth. Fill the third bowl with the panko breadcrumbs. Line two shallow baking sheets with parchment paper.

Cube the mozzarella: Cut the mozzarella into 18 to 20 cubes, each about ½ inch in size. Keep them chilled in the refrigerator so they remain firm until you’re ready to use them.

Finish the rice: When the rice is soft and fully absorbed the broth, turn off the heat and fold in the grated parmesan. Transfer the hot rice to one of the parchment-lined baking sheets, spreading it out evenly. Let it cool for about 10 minutes until it is cool enough to shape.

Stuff the rice: Once the rice has cooled slightly, scoop and shape it into 18 round balls, each roughly 1 inch in diameter. Use your hands or a small cookie scoop for uniformity. Press a mozzarella cube into the center of each rice ball, molding the rice around it to fully enclose the cheese.

Bread the arancini: Roll each rice ball first in the flour mixture, then coat it in the beaten eggs, and finally roll it through the panko. Press lightly to help the breadcrumbs adhere. Arrange the breaded balls on the second parchment-lined sheet.

Fry: Heat the grapeseed or vegetable oil in an 8-inch saucepan until it reaches 350°F. The oil should be about ½ inch deep. Fry 6 arancini at a time, turning gently to brown all sides evenly. They will become golden and crisp in about 3 to 4 minutes. Transfer them to a paper towel-lined plate to drain excess oil.

Serve: Allow the arancini to cool for 5 minutes. Serve warm with toothpicks or alongside napkins for easy snacking.