Bring a large (4-quart) pot of water to a boil over medium-low heat and add 1/2 tablespoon salt and the Arborio rice. Cook, stirring occasionally, for 20 minutes. The grains of rice will be quite soft. Drain the rice in a sieve and run under cold water until cool. Drain well.

Meanwhile, whisk together the yogurt, eggs, chives, fontina, 1 1/4 teaspoons of salt, and the pepper in a medium bowl. Add the cooled rice and mix well. Cover with plastic wrap and refrigerate for 2 hours or overnight, until firm.

When ready to cook, preheat the oven to 250 degrees F.

Spread the panko in a shallow dish. Heat 3 tablespoons of olive oil in a large skillet over medium-low heat. Form balls of the rice mixture using a standard (2 1/4-inch) ice-cream scoop or a large spoon. Pat the balls into patties 3 inches in diameter and 3/4-inch thick. Place 4 to 6 patties in the panko, turning once to coat. Place the patties in the hot oil and cook, turning once, for about 3 minutes on each side until the risotto cakes are crisp and nicely browned. Place on a sheet pan lined with parchment paper and keep warm in the oven for up to 30 minutes. Continue cooking in batches, adding oil as necessary, until all the cakes are fried. Arrange on a serving platter and serve hot.