It's time for fresh asparagus soup

This Feb. 16, 2011 photo shows roasted asparagus and potato soup in Concord, N.H. For this soup recipe, all the vegetables are roasted at high heat, caramelizing their natural sugars and enhancing the flavors. They are then pureed until smooth and combined with thick, nonfat Greek-style yogurt, which gives the soup a creamy quality that belies its low-fat nutritional profile. (AP Photo/Matthew Mead)

Global markets and high-tech shipping methods have put asparagus on our tables virtually year-round, yet most of us still associate it with spring.

But whenever you eat it, asparagus is a nutritional powerhouse. It is low in calories (about 5 calories per stalk) and is packed with vitamins A, C and E and folate.

Green, purple and white varieties of asparagus are common, though green is the least expensive and most readily available. Green asparagus has a fresh, woodsy flavor, while purple varieties tend to have a more fruity flavor. White asparagus is milder in flavor and should always be peeled before cooking.

When shopping for asparagus, look for firm stalks with tight tips. Fresh asparagus should snap when bent. It can be refrigerated, wrapped in a damp cloth inside a plastic bag, for three days.

Though not essential, peeling tough-skinned stalks with a vegetable peeler will help ensure that the tips and otherwise thicker stalks cook at the same rate. And be sure to rinse all asparagus thoroughly before cooking to remove any lingering sand.

For this simple asparagus and potato soup, all the vegetables are roasted at high heat, caramelizing their natural sugars and enhancing the flavors. They then are pureed until smooth and combined with thick, nonfat Greek-style yogurt, which gives the soup a creamy quality that belies its low-fat nutritional profile.

To top off the soup, shreds of sweet and salty prosciutto ham are

crisped in a skillet to create a garnish that has all the appeal of crumbled bacon, without all the grease.

ROASTED ASPARAGUS AND POTATO SOUP

6 cloves garlic

1 1/4 pounds asparagus, bottoms trimmed and cut into 1-inch pieces (about 3 cups)

2 cups peeled and diced Yukon Gold potatoes

1 medium sweet onion, cut into 6 wedges

1 tablespoon extra-virgin olive oil

1/2 teaspoon salt, plus more to taste

1/2 teaspoon ground black pepper, plus more to taste

2 ounces prosciutto, chopped

3 cups chicken broth

6 ounces nonfat plain Greek-style yogurt

1 teaspoon lemon juice

1 tablespoon minced fresh tarragon

Place garlic on a square of foil and sprinkle with 1 teaspoon water. Fold foil into a packet. Set aside.

In a large bowl, combine asparagus, potatoes, onion, oil, 1/2 teaspoon salt and 1/2 teaspoon of black pepper. Toss to coat. Spread vegetables over 2 large, rimmed baking sheets. Place packet of garlic in one corner of one of the sheets. Place baking sheets in a preheated 425-degree oven and roast vegetables, stirring occasionally, until asparagus pieces are soft and potatoes are tender, 35 to 45 minutes.

Meanwhile, in a small skillet over medium heat, crisp prosciutto, about 5 minutes per side.

When vegetables are roasted, empty garlic (remove peel) onto the baking sheet with the other vegetables and cool for 5 minutes.

Transfer half of vegetables into a blender. Add 1 1/2 cups broth, then blend until smooth. Transfer to a large pot. Repeat using remaining vegetables and remaining 1 1/2 cups of broth. Warm soup over medium heat.

Whisk yogurt, lemon juice and tarragon into soup. Season with salt and pepper to taste. Crumble prosciutto and use to top each serving. Makes 4 servings about 233 calories each.

Kristin Kreuk Sarah Silverman Thandie Newton Halle Berry Sunny Mabrey