This is a treasure from northern Italy's Emilia-Romagna region and my favorite type of mostarda. It is similar to a fruit preserve that's not only fruity but, sweet, spicy with a touch of acidity. This makes it the perfect accompaniment to many foods, especially those with a little fat like Parmigiano-Reggiano cheese, pork, and duck.
In the summer when the fruits come to their peak flavor I make several kinds of mostarda. My favorite is cherry followed by rhubarb mostarda, a close second. I make small batches so it is a quick summer project. Now you have a new summer project that will pay dividends in the winter months when you serve roast pork or duck breast.