(acceptable, if inauthentic, stand-ins include duck fat and olive oil)
, soaked overnight and drained
Coarse salt and white pepper, (such as parsley, chives, and/or thyme)
, sliced 2 inches thick (optional)
In a stock pot over medium heat, melt the goose fat. Add the onions and garlic and cook until tender but not browned, about 10 minutes.
Stir in the flour until it forms a smooth paste. Still stirring constantly, slowly add half of the stock. Continue stirring until the mixture begins to thicken. Stir in the remaining stock and the beans. Reduce the heat to medium-low and simmer for 45 minutes. Let cool for 10 minutes.
Working in batches, pour the soup into a blender and process until smooth. Return the soup to the stock pot and place over medium-low heat. Add the cream and season with salt, white pepper, and the herbs. Adjust the heat until the soup is just simmering and then slowly stir in the vinegar. Ladle the soup into a tureen or bowls. Float large pieces of the bread on top, if using, and serve right away. And if you are bringing the soup to newlyweds, don’t forget to knock!