A humble note from the Surreal Gourmet: the payoff from the purple potatoes is somewhat underwhelming. If purple potatoes are easily available, by all means use them. Otherwise, substitute with Yukon gold potatoes.
- 1 whole bulb garlic
- 1 teaspoon olive oil
- 1 tablespoon butter
- 2 large leeks, white and light green parts only, coarsely chopped and thoroughly washed
- 1 cooking onion, chopped
- 3/4 cup dry white wine
- 8 purple potatoes, or 4 medium Yukon gold or russet potatoes, peeled and sliced or diced
- 6 cups vegetable broth or chicken stock
- 1/2 teaspoon salt
- 1/2 teaspoon white pepper
- 4 sprigs fresh sage, or 1 tablespoon dried sage
- 3 cups whole milk
Preheat the oven to 350 degrees F.
Cut off the top 1/4 of the pointy end of the garlic bulb so that all of the cloves are exposed. Drizzle with olive oil, wrap in aluminum foil and bake for about 1 hour, or until the top is browned and the individual cloves are soft throughout. Let cool.
Melt the butter in a soup pot over medium-high heat. Add the leek and onion and stir for about 5 minutes, or until they are translucent but not yet brown. Add the wine and cook for 2 more minutes.
Add the potatoes and stock. Bring to a boil, then reduce heat to medium-low and simmer for 40 minutes. (Adjust heat as required to simmer.)
Add the salt, pepper, and sage. Let the soup cool.
Just before serving, add 1 part milk for every 3 parts soup, and blend in a blender for 15 seconds to aerate. Serve cold in chilled bowls.