To make the aioli, in the bowl of a food processor, combine the yolk, lemon juice and vinegar. With the machine running, slowly add the olive oil until emulsified. Transfer to a bowl and stir in the miso. Cover and refrigerate until ready to serve.

To make the arancini, preheat oven to 350°F. Line a baking sheet with parchment paper. Place the carrots on the prepared baking sheet and bake until soft, 45–60 minutes. Let cool, then purée in a food processor until smooth.

In a medium saucepan, combine the vegetable stock and half of the carrot purée and bring to a simmer over medium-low heat.

Meanwhile, in another saucepan, warm the olive oil over medium-low heat. Add the onions and sauté until translucent, 2–3 minutes. Add the wine and cook, stirring, for 2–3 minutes. Add a ladleful of the broth mixture to the rice and cook, stirring, until incorporated. Continue stirring in the broth, one ladleful at a time and stirring until incorporated before each new addition, until the rice is tender, about 20 minutes. Stir in the remaining carrot purée. Season to taste with salt and pepper. Spread the risotto over the parchment-lined baking sheet and refrigerate overnight.

To form the arancini, use a small scoop to form the risotto into balls. Press a piece of mozzarella into each risotto ball. Using damp hands to prevent sticking, roll each ball between your palms to enclose the cheese.

Set out 3 shallow bowls: Add the flour to bowl 1, the eggs to bowl 2 and the panko to bowl 3. Season the flour and panko with salt and pepper. Lightly whisk the eggs.

Working with one arancini at a time, coat first in flour (tapping off the excess), then in egg, then in panko. Set aside in a single layer until ready to cook.

Pour 6 inches of oil into a heavy-bottomed pot. Place over medium heat and heat to 350°F on a deep-frying thermometer. Add 6–8 arancini and cook, turning as needed, until evenly browned, 3–4 minutes. Using a slotted spoon, transfer to a paper-towel-lined plate, and continue to cook the remaining arancini. Grate the Pecorino Romano over the arancini.

To serve, arrange the arancini on a serving platter. Dot miso aioli on both sides of each arancini. Place 2 pickled carrot slices between each arancini. Season the pea purée with salt and pepper, then dot the pea purée between the carrots and miso. Garnish with nasturtium.