Place stock in a small saucepan and bring to a simmer. Reduce heat to keep hot.

Melt butter in a large saucepan over medium heat. Add onion and garlic, sprinkle with salt, and cook until translucent and tender, but not browned, about 5 minutes.

Add arborio rice, stir to coat, and add wine. Cook, stirring continuously, until wine is absorbed.

Add stock, 1/3 to 1/2 cup at a time, stirring and cooking until completely absorbed before adding more. Continue adding stock until the rice is nearly done -- it'll still be crunchy in the very center -- then add the vegetables along with the stock.

Once the rice is done - it should still be chewy in the center - stir in cheese, cover, and remove from heat. Let stand 5 minutes before seasoning to taste with salt and pepper.

Serve with a drizzle of fennel oil and additional grated cheese on top.