Heat a heavy-bottomed pot over medium-high heat.
Add one tablespoon of the extra virgin olive oil, shallots, and garlic, sautéing until translucent.
Add the rice and sauté until translucent.
Add 1/4 of the chicken stock, stirring constantly until it is absorbed.
Continue to add the stock,1/4 at a time, stirring constantly, until all of it is absorbed and the rice is tender.
Transfer the rice to a sheet pan, spread it out in a thin layer, and allow to cool.
While the rice is cooking, brown the sausage in a large skillet.
Add the mushrooms and cook until all of the water is released and evaporated.
Drain the mixture and allow to cool completely.
Pulse the sausage and mushroom mixture in the bowl of a food processor until just chunky, then add the mozzarella and pulse a few times to just incorporate. Reserve.
While the rice is cooling, heat a heavy sauce pot over medium-high heat.
Add the remaining extra virgin olive oil and when it begins to shimmer, add the onions, stirring occasionally.
When the onions are just before burnt, remove them with a slotted spoon. Discard onions and add tomatoes to the pot, stirring often to break up the tomatoes.
Once the confit is at desired consistency, remove from the heat and add the zest. Reserve.