- 2 tablespoons unsalted butter
- 1/4 pound French baguette, crusts removed, bread cut into 1/2-inch dice
- 2 ounces smoky bacon, cut into 1/4-inch dice
- 1 medium onion, cut into 1/4-inch dice
- 1/2 cup dry white wine
- 1 1/2 quarts chicken stock or canned low-sodium broth
- 1 garlic clove, minced
- 1/2 pound Yukon Gold potatoes, peeled and cut into 1/4-inch dice
- Salt and freshly ground pepper
- 1 1/2 tablespoons fresh lemon juice
- 1/4 teaspoon finely grated lemon zest
- 3 tablespoons crème fraîche or heavy cream
- 1/2 pound sorrel, stems discarded, leaves coarsely chopped
- Melt 1 tablespoon of the butter in a large skillet. Add the diced baguette and cook over moderately low heat until browned on the bottom, about 3 minutes. Stir the croutons and cook until crisp all over, about 2 minutes longer. Transfer to a plate to cool.
- Melt the remaining 1 tablespoon of butter in a large saucepan. Add the bacon and cook over moderately low heat until lightly browned, about 4 minutes. Add the onion and cook until softened, about 7 minutes. Add the wine and simmer until almost evaporated, about 4 minutes. Add the stock and garlic and bring to a simmer. Add the potatoes, season with salt and pepper and cook until tender, about 10 minutes. Stir in the lemon juice and zest and the crème fraîche and simmer for 2 minutes. Remove from the heat and stir in the sorrel. Season with salt and pepper. Ladle the soup into bowls and serve; pass the croutons at the table.
The croutons can be made a day ahead. Store in an airtight container. The soup can be made without the sorrel and refrigerated overnight. Bring to a simmer and add the coarsely chopped sorrel just before serving.