Riesling Onion Soup with Herbed Croutons

In a large, wide saucepan or soup pot over medium heat, melt the butter. Add the onions, leeks, garlic and tarragon and cook, stirring often, until the onions are soft and golden, about 15 minutes. Sprinkle in the flour and cook, stirring constantly, for 3 minutes more. Pour in the wine, bring to a simmer and cook until reduced by half, about 10 minutes. Pour in the stock, return to a simmer, reduce the heat to low and cook, uncovered, until reduced slightly, about 45 minutes. (The soup can be made up to this point up to 24 hours in advance and stored, tightly covered, in the refrigerator. Reheat gently before continuing.) Season with salt and pepper.

To make the herbed croutons, preheat an oven to 300°F.

Arrange the baguette slices in a single layer on a rimmed baking sheet. In a small bowl, stir together the olive oil, butter and herbs. Lightly coat each bread slice on both sides with the oil mixture. Toast the bread in the oven, turning occasionally, until crisp and golden brown, 15 to 20 minutes. Remove from the oven and set aside. (The croutons can be made up to 24 hours in advance and stored, tightly covered, at room temperature.)

Preheat a broiler.

Arrange individual ovenproof bowls on a baking sheet and ladle the soup into the bowls. Top each serving with 2 or 3 croutons and an equal amount of the cheese. Place the baking sheet under the broiler 7 inches from the heat source and broil until the cheese melts, about 1 minute. Remove from the broiler and serve immediately. Serves 6.