- 4 large shallots, chopped
- 2 tablespoons unsalted butter
- 1 tablespoon olive oil
- 2 teaspoons curry powder (preferably Madras)
- 3 cups reduced-sodium chicken broth
- 2 cups water
- 2 (10-ounce) packages frozen peas
- 1 (3/4-pound) bunch spinach, stems discarded (about 8 cups packed leaves)
- 1 cup well-shaken buttermilk
- Cook shallots in butter and oil in a heavy medium pot over medium heat, stirring, until golden, 6 to 8 minutes. Add curry powder and 3/4 teaspoon salt and cook, stirring, 1 minute. Add broth and water and bring to a simmer, then stir in peas and spinach and return to a simmer. Cook, uncovered, stirring occasionally, until vegetables are just tender, about 6 minutes.
- Immediately purée soup in 4 batches in a blender until very smooth (use caution when blending hot liquids). Transfer to a bowl and stir in buttermilk. Quick-chill (to preserve color) by setting bowl in an ice bath and stirring until cool, then refrigerate until very cold, 1 to 2 hours. Season with salt.