The creaminess of this soup is absolutely astounding when you consider it doesn’t contain a lick of heavy cream or half-n-half. The secret is using fully mature plum tomatoes and sautéing the mirepoix on very, very low heat for a good half hour. —Serena Cosmo of Rustic Plate
If you’re using fresh tomatoes, bring a large, heavy pot filled with water to a boil. Add the tomatoes and allow them to cook for a minute. Remove them immediately and allow them to cool enough for you to handle them. Then, remove the skin of each tomato. Cut each tomato in half and remove the seeds with your fingers. Set aside.
In the same pot, heat the butter over a medium-low flame. Add the roughly chopped vegetables with a good pinch of salt and lower the flame to low. Sauté for 30 minutes, stirring often. It may seem like a lot of cooking, but don’t be tempted to turn up the flame to make this process go faster. This step slowly brings out the natural sweetness of the onion, celery and carrot, and rushing this process can make them taste bitter instead.
Add the fresh tomatoes halves, the broth, the nutmeg, the sugar and a little more salt. Stir well and increase the heat to medium high to bring it to a boil. Once that happens, lower the flame to low and allow to gently cook, with peaceful bubbling in the pot, for 1 to 2 hours. I’ve found that the longer I cook it, the tastier the soup is.
Puree the mixture with an immersion blender. Add the Parmigiano-Reggiano and mix well into mixture with a spoon or ladle. Ladle out the soup into bowls and top with fresh basil leaves, either whole or gently ripped.