Cut with a knife the side of each blossom and stuff with one cube of mozzarella and a piece of anchovy. Place on a large platter and set aside.
Pour 3 inches of oil in a large wok or large heavy pot and heat to 375 F.
In a large mixing bowl, add the flour, baking powder, and sparkling water and mix until the batter is the consistency of heavy cream.
Dip 2 zucchini flowers at a time in the batter to coat completely, and let the excess batter drip off.
Fry the flowers in the hot oil for 1 minute on each side, gently rolling them with the help of a spatula, until crisp and golden brown. Pull gently out of the oil, set them on a platter lined with paper towels, and season with salt and pepper while they are still hot.
Repeat the steps with the remaining zucchini flowers.