Risotto is a classic Italian dish that, like pasta, can be done in a million different ways. Here, we're using some of summer's best produce: ripe tomatoes and green zucchini. Risotto is very much about technique. You want to get the consistency and texture exactly right, so it's creamy but still al dente. Here's how.
Mince the onion, keeping the onion pieces about the same size as the rice grains. Dice the zucchini, reserving the ends.
Remove the tomatoes from the oven. Discard the basil leaves. Purée the tomatoes in a food processor or by hand by chopping and mincing the tomatoes on a cutting board until no chunks remain. Set aside ½ cup of Tomato Purée. (Reserve the remainder for another use.)
Melt 2 tablespoons of cold butter in a saucepan over low heat. Add the onions and cook very slowly, until the onion is tender but has taken on no color. In a separate sauce pot, bring vegetable stock to a simmer, and infuse with the zucchini ends and basil stems.
Add the rice to the butter and onion soffritto and toast, stirring with a spoon, for about 4 minutes. Toast at a low heat; do not let the rice take on color. When the rice is toasted and the grains are a nice white color, add the wine and cook over moderate heat until all the wine is reduced. Set a timer to 16 minutes. Start adding the hot stock to the rice, one ladle at a time, just covering the rice. Repeat, adding more stock, each time the liquid has absorbed into the rice. Continue to stir after each addition of stock and wine. (Note: At the eight-minute mark, move on to step 6.)
At the eight-minute or halfway mark, add the zucchini. Continue cooking for the final eight minutes while adding the remaining stock. Dice the remaining cold butter and set aside. When the timer goes off, let the rice rest for about thirty seconds but no more, to prevent cooling. Finish by adding the Parmigiano-Reggiano, Tomato Purée, diced butter, and squash blossoms (optional); then stir.
Season with the salt and adjust the rice with some warm stock if necessary. The final consistency should be creamy and spread slowly on the plate. Serve immediately on warmed plates. Garnish with a chiffonade of mixed basil leaves.
Tomato Puree (optional)
(Note: If you want to skip making the Tomato Puree, combine 1/2 cup of plain tomato sauce with 1 grated clove of garlic.) Preheat oven to 325 degrees F. Core the tomatoes. With a sharp knife, cut the tomatoes through the equator and lay cut side up on a half-sheet pan fitted with a wire rack. Season the tomatoes with the salt evenly. Cut the garlic into thin slices and place a slice of garlic on each tomato half. Finish with some basil chiffonade on each tomato. Drizzle the tomatoes with olive oil and roast in the oven, 1 1/2 hours.