Whenever Jim Peterson takes on a topic, he does it thoroughly and with care.

He is the author of "Sauces: Classical and Contemporary Sauce Making" (the 1991 James Beard Cookbook of the Year Award), "Splendid Soups" (nominated for a James Beard Award in 1994) and "Fish & Shellfish" (a Julia Child Cookbook award-winner in 1997 for best single subject cookbook).Peterson's most recent is "Vegetables" (Morrow, $35). So I knew I was dealing with no cookbook slouch when, armed with the book and tagged recipes, I recently had the pleasure of a shopping trip with Peterson through New York City's Union Square Greenmarket.

My mission was to select the best produce with the author, to test his recipes for this article.

It was a gray, drizzly day in the Big Apple, but the greenmarket's beautiful produce was abundant enough to inspire these two foodies to select ingredients for a delicious recipe-testing dinner experience.

I had tagged a couple of tomato gratin recipes, and as we strolled by one market stand the fragrant aroma of some cherry tomatoes beckoned to us.

"I do a lot of shopping by smell," Peterson remarked. "Sometimes you just can't smell the produce at the supermarket. In the case of tomatoes, I look for tomatoes that smell great and feel sort of rough on the outside. This shows that some of the natural sugars have developed.

"Also, you need to think about what you are using the tomatoes for. In gratins, I look for firmer-textured tomatoes. Mushy tomatoes give off too much liquid in the cooking. Softer tomatoes could be a good choice when used in sauces. Out-of-season cherry tomatoes often still have a sweet flavor.

"In my book, the hors d'oeuvre recipe for Slow-Baked Cherry Tomatoes with Herbs makes good use of the larger, grocery-store-type cherry tomatoes. I don't especially care for sun-dried tomatoes, and these make a good substitute. You can serve them as is, or use them as a spread on bread."

I was convinced I must have those cherry tomatoes and I decided to make the recipe for dinner. They were sweet and tangy with an intense tomato flavor.

In the book, Peterson reveals that this recipe was a result of a student's having left a tray of baked cherry tomatoes in the oven for too long. Peterson took a bite and realized that one of "the sad and wizened little mistakes" had merit. His innovation was to cut the tomatoes in half and bake them with a drizzling of olive oil, Parmesan cheese, garlic and fresh chopped herbs.

As we walked through the market, Peterson suggested some other food combinations. A fine bunch of lavender prompted him to mention that he likes to saute zucchini in oil with garlic and lavender to add a lovely herbal-floral flavor. He cautioned that without the garlic it could have a soapy taste.

Perfect small purple onions drew the comment that "they would be great glazed or skewered and cooked on the grill until they are charred on the outside with a sweet melting quality on the inside."

As we inhaled the fragrance of basil leaves, Peterson said he loves to combine the leaves and arugula tossed with olive oil, vinegar, salt and pepper for a simple salad.

At a stand of sorrel, Peterson described one of the soups in his book, a basic leek, onion and potato soup with 15 variations that was especially delicious with sorrel. On that rainy day, his description of sorrel adding a bright, tangy, lemony quality to soup sounded good.

In the book, Peterson devotes a whole section to Vegetable Creamed Soups, pointing out that "most creamed soups, especially when made with milk, are creamy enough without the cream or with very little cream."

The soup was creamy and satisfying, and even though I bought cream for the recipe, I ended up not using any of it. The soup was great served chilled the next day.

I asked Peterson if he felt especially healthy while he was testing these vegetable recipes. His honest answer made me laugh: "No, after a day of testing, I would say to my assistant, `Let's go out for a steak!' "

The book has more than 425 pages with full-color photographs taken by Peterson. Graphically, it is beautiful and easy to use.

It starts with an overview of how to handle and cook vegetables. Next, each vegetable is described along with instructions for its preparation. The rest of the book is devoted to explicit recipes covering almost every aspect of vegetable cookery.

Most appealing is the sense it gives of Peterson's immense knowledge via his useful headnotes and boxes. Like the author in person, his writing is approachable, friendly and en-thu-siastic.

It's a book that you can pick up again and again and learn something new every time.

The 47-year-old Peterson, who now lives in Brooklyn, grew up in northern California. After majoring in chemistry with a minor in philosophy at the University of California at Berkeley, he took a year off to travel around the world, ending up in the south of France picking grapes for a family of winemakers.

Impressed by the foods of France, Peterson decided he wanted to cook professionally. He returned to the United States for two years, working in restaurants to save money for a prolonged stay in France and for cooking school.

After two more years in France, cooking at two three-star restaurants, he returned to the United States. He worked at Le Petit Robert in Greenwich Village, cooking innovative yet rustic traditional French food. He went on to teach in New York City at the French Culinary Institute and later at Peter Kump's cooking school.

He plans to do a photo book on cooking techniques next.

*****

RECIPES

SLOW-BAKED CHERRY TOMATOES WITH HERBS

30 cherry tomatoes, stems removed (increase the number to 45 if the tomatoes are small)

3 tablespoons extra-virgin olive oil

1 garlic clove, minced

2 teaspoons finely chopped fresh marjoram, thyme and/or oregano, or 1 teaspoon dried

2 tablespoons freshly grated Parmesan cheese

Salt

Heat the oven to 300 F.

Cut the cherry tomatoes in half crosswise and squeeze the seeds out of each half. Brush a baking dish large enough to hold the tomatoes in single layer with a thin coating of the olive oil. Arrange the tomatoes, flat side up, in the dish. If the tomatoes don't stay upright in the dish, make a tiny slice on the bottom of each one so they rest flat.

Crush the chopped garlic with the side of a chef's knife on a cutting board until you obtain a smooth paste. In a small bowl, combine the garlic with the remaining olive oil, the herbs and Parmesan cheese.

Use a small spoon to drizzle the olive oil mixture into each of the tomatoes. Sprinkle the tomatoes with salt and bake for about 2 hours, or slightly less if your tomatoes are extremely small. The tomatoes should be shriveled and lightly browned around the edges. Makes 15 hors d'oeuvres servings.

BASE FOR CREAMED SOUPS

3 tablespoons butter

1 medium onion, or whites from 4 medium leeks, minced

1 large Idaho potato (12 ounces), peeled and cut into 1/4-inch-thick slices

6 cups milk, chicken broth or a combination

Chosen vegetable (see following)

1/4 to 1 cup heavy cream (optional)

Salt and freshly ground black pepper

Heat the butter in a 4-quart nonaluminum pot over medium heat. Add the onion and cook, stirring, until it turns translucent, about 8 minutes. Add the potato slices and the milk or broth and bring to a gentle simmer. Simmer for about 20 minutes or until the potato and vegetable have completely softened and are easy to crush against the side of the pot with the back of a fork. Add the vegetables, following the recipe, according to how long it takes to cook.

Most of the time, vegetable creamed soups are best when quickly pureed in a blender and then worked through a food mill or through a medium-mesh strain-er with the back of a ladle.

Heat the soup, add as much cream as you like, and season with salt and pepper. Makes 8 to 12 cups of soup, depending on the vegetable.

Cream of Broccoli Soup

Remove the florets from two 1-pound bunches of broccoli and reserve 8 florets for decorating the soup. Boil the 8 florets for 4 minutes, drain, and rinse with cold water.

Prepare the soup base. When the potato has softened, stir in the uncooked florets and simmer gently for 7 minutes. Puree in a blender and work through a food mill or through a strainer with the back of a ladle. Thin the soup if necessary with additional liquid. Finish the soup with the optional cream and the salt and pepper. Decorate each bowl of soup with a reserved floret. Makes 8 servings without the cream.

Cream of Sorrel Soup

Prepare the soup base as directed, but use twice the amount of potato. When the potatoes are completely cooked, stir 1 pound of sorrel into the soup and simmer for 5 minutes. Puree in a blender and strain through a food mill or medium-mesh strainer with the back of a ladle. If you want the soup very smooth, strain it again through a fine-mesh strainer. Finish the soup with the optional cream, and salt and pepper. Thin if necessary with extra broth or milk. Serve hot or ice cold. Makes 8 servings without the cream or additional liquid.

Cream of Tomato Soup

The best cream of tomato soup is the simplest, made with the best, ripest tomatoes you can find.

Peel, seed and chop 5 pounds of very ripe tomatoes (about 15 medium). Heat the chopped tomatoes in a pot over medium-low heat and when they come to a simmer stir in 1/2 to 2 cups cream. Bring back to simmer and season to taste with salt and pepper. Makes 8 servings.

- Recipes adapted with permission from "Vegetables" by James Peterson (Morrow, 1998, $35).