1
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In a heavy soup pot, melt the butter over medium-low heat and swirl to coat the pot bottom. |
2
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Add the leek, onion, carrot, and salt and stir briefly. |
3
|
Cover and cook, stirring once or twice, until the vegetables are very soft but not brown, about 20 minutes. |
4
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Uncover, add the potato, water, sugar, and pepper, increase the heat to medium-high, and bring to a simmer. |
5
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Adjust the heat to maintain a simmer, re-cover, and cook, stirring occasionally, until the vegetables are tender when pierced with a fork and soft enough to purée, about 35 minutes. |
6
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Add the radish tops and stir until the greens are wilted, about 1 minute. |
7
|
Remove from the heat and let the soup cool for about 10 minutes. |
8
|
Working in batches, process the soup to a smooth purée in a blender or food processor. (At this point, the soup can be cooled, covered, and refrigerated for up to 2 days.) |
9
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Return the puréed soup to the pot and place over medium-low heat. If the soup is too thick, add a little water to achieve a creamy consistency. |
10
|
Heat until steaming hot, stirring occasionally. |
11
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To serve, ladle the soup into warmed bowls. |
12
|
Place a little clump of matchstick-cut radishes in the center of each bowl for garnish. |
13
|
Serve immediately. |