Trim and discard zucchini ends. Working with the 3 widest, cut across width into 2inch lengths. Using a melon baller or small spoon, scoop out inner meat and seeds of each 2-inch piece, leaving a thin base at bottom so "boat" stands for stuffing. Place scooped-out centers into a food processor.
Roughly chop remaining zucchini. Add to food processor and puree until well chopped.
Bring a medium pot of salted water to a boil. Blanch zucchini boats just until they begin to soften, about 2 minutes. Immediately refresh in a bowl of iced water. Drain and arrange, flatside down, in a large jelly roll pan or roasting pan.
Preheat oven to 375 degrees F.
Melt butter in a medium saucepan over medium-high heat. Add reserved chopped zucchini and saute until liquid is evaporated, about 15 minutes. Stir in nuts, cook for 1 minute, then add cream, salt, and pepper. Bring to a boil. Cook until cream thickens, about 3 minutes. Add 1/2 cup Parmesan cheese and all bread crumbs. Remove from heat and stir until smooth.
Using a tablespoon or pastry bag fitted with a plain tip, stuff zucchini boats with cream mixture. Pour boiling water into pan containing filled zucchini boats until it rises about 1/4-inch, to form a water bath. Bake 15 minutes.
Heat broiler. Sprinkle remaining Parmesan cheese over tops and place under broiler until slightly golden, about 1 minute. Serve immediately.
c.1997, M.S. Milliken & S. Feniger, all rights reserved