Cream infused with the flavor of toasted hazelnuts (filberts) gives elegance to this sauce for fettuccine. A combination of green spinach noodles and more toasted nuts, slivers of smoked trout, and lemon peel, the dish makes a stunning first course or entree.

At San Francisco's Old Poodle Dog Restaurant, where this dish is served, it is flamed with hazelnut liqueur to intensify the fragrance; the step is optional here. Spinach Fettuccine in Toasted Hazelnut But Sauce with Smoked Trout 1-1/3 cups (about 6 oz.) hazelnuts 1 lemon water 2 tablespoons salad oil 1 large onion, thinly sliced About 2 cups whipping cream 1 cup (1/2 lb.) unsalted butter or margarine 1/4 cup hazelnut-flavored liqueur (optional) 1 pound fresh or 12 ounces dry spinach fettuccine 4 to 8 ounces smoked boned trout, skinned and cut into 1/4-inch-wide strips 2 Tablespoons chopped parsley Lemon wedges

Place nuts in a 10- by 15-inch pan and bake in a 350[deg.] oven until golden underneath skin, about 15 minutes. Wrap nuts in a towel and rub briskly to remove most of the skins. Lift out and chop nuts.

With a vegetable peeler, remove peel (yellow part only) from lemon. Cut peel into julienne strips. In a 1- to 2-quart pan, bring 2 cups water to boiling. Add peel and simmer, uncovered, 5 minutes; drain. Set peel aside. Juice lemon and set aside for sauce.

In a 10- to 12-inch frying pan, combine oil and onion, stirring over medium-low heat until onion is very limp and slightly gold. …