Soak the vegetable strips in a bowl of ice cubes and water for an hour to crisp them. Pat dry with paper towels and arrange on a platter with the romaine leaves, tomatoes and mushrooms. Cover with plastic wrap and refrigerate.

Arrange the bread sticks on a separate plate and set aside.

In a heavy 1-quart enameled or stainless-steel saucepan, bring the cream to a boil and cook it, stirring frequently, for about 15 to 20 minutes, or until it has thickened and has reduced to about 1 cup. This process may take much longer; especially if you are doubling or tripling the recipe for a large party.

Choose a 3- or 4-cup enameled or flameproof earthenware casserole that fits over a candle warmer, spirit lamp or electric hot tray. On the stove, melt the butter in the casserole over low heat; do not let it brown. Add the anchovies and garlic, then the reduced cream and truffle, and bring the sauce to a simmer, stirring constantly. Do not let it boil. Serve the Bagna Cauda at once, accompanied by the cold vegetables and the bread sticks.

To eat, pick up a vegetable or bread stick with your fingers and dip it into the hot sauce. If the butter and cream separate as the sauce stands, beat with a wire whisk. (If you are serving this for a crowd, which is a good time to serve it, just leave a whisk on the serving board next to the casserole; guests tend to take care of it.)

You may substitute / add almost any raw vegetable you like for Bagna Cauda: fennel sticks, cauliflower or broccoli flowerets, white turnip wedges, or radishes.