*Available at Italian markets and some cheese shops.
Directions
Cook broccoli in large saucepan of boiling salted water until crisp-tender, about 4 minutes. Using slotted spoon, transfer broccoli to bowl of ice water and cool. Drain well. Return water in saucepan to boil. Add potato; cook until tender, about 15 minutes. Drain. Transfer broccoli to food processor and blend well. Add potato and process to puree. Add 1/2 cup broth and blend well. With machine running, gradually blend in extra-virgin olive oil. Season to taste with salt and pepper. DO AHAED: Broccoli sauce can be made 1 day ahead. Cover and refrigerate.
Using electric mixer, beat ricotta in large bowl until smooth. Beat in mozzarella. Form mixture into 6 rectangular dumplings, each about 3 1/2 x 2 x 3/4 inches. Place on baking sheet; cover and refrigerate 4 hours.
Pour enough olive oil into very large skillet to reach depth of 3/4 inch. Heat oil to 350°F. Whisk 1 1/2 cups water, yolk, and pinch of salt in large bowl; whisk in 3/4 cup flour. Set batter aside. Place remaining 1 cup flour in medium bowl. Coat each dumpling in flour, turning to coat. Dip into batter, then fry until very pale golden, about 3 minutes per side. Using slotted spoon, transfer to paper towels to drain.
Bring broccoli sauce to simmer in medium saucepan, thinning with more vegetable broth if necessary.
Spoon 1/3 cup sauce into center of each of 6 plates; spread with back of spoon into round. Top each with 1 dumpling.
