2 tablespoons extra-virgin olive oil
1 medium onion, finely chopped
1-1/2 cups Arborio rice
3/4cup dry white wine
4 cups chopped fresh spinach leaves
1/2cup freshly grated Parmesan cheese, plus more for garnishing
freshly ground black pepper
5-7 cups vegetable broth
3 large eggs
2 cups fresh breadcrumbs
2/3 cup toasted walnuts, finely ground
Savory tomato sauce
Make the risotto ahead: Heat the oil in a heavy-bottomed large saucepan over medium heat until shimmering. Add the onion and a pinch of salt and cook until translucent, about 5 minutes.
Stirring constantly with a wooden spoon, add the rice and cook for 1 minute. Add the wine and cook, stirring often, until the wine nearly evaporates, about 2 minutes. Add 1 cup of the hot broth and cook, stirring often, until the rice absorbs the liquid. Continue adding the hot broth in 3/4-cup increments and stirring often until the rice is nearly tender, about 20 minutes. Stir in the spinach and continue to add broth as necessary until the rice is creamy (not soupy) and soft but still a bit al dente, about 5 minutes. Remove from the saucepan and stir in the cheese. Adjust the seasonings, adding salt and pepper to taste. Chill at least 4 hours or overnight.
Make the cakes: Move an oven rack to the middle position and heat the oven to 425 degrees. Brush the remaining 2 tablespoons oil over a large rimmed baking sheet. With a fork, lightly beat the eggs in a shallow bowl. Combine the breadcrumbs and walnuts in a second shallow bowl. Shape 1/4 cup of the chilled risotto into a 3-inch round. Dip the risotto cake into the eggs and then into the breadcrumb mixture. Shake off the excess breadcrumb mixture and place the breaded risotto cake on the oiled baking sheet. Repeat with the remaining risotto to make a total of 12 risotto cakes.
Bake the risotto cakes, turning them once, until golden brown, 20 to 25 minutes. Serve immediately.
Savory Tomato Sauce: Sauté 1/2 cup onions and 2 cloves chopped garlic. Mix with 1 large can tomatoes, 1/2 cup Sonata wine, salt and pepper. Puree in food processor. Serve warm as a sauce for the risotto cakes.