White Onion Soup with Chive Oil

1. 1

   Have ready a bowl of ice and cold water.

2. 2

   In a saucepan of boiling water blanch chives 10 seconds and drain in a sieve.

3. 3

   Immediately plunge chives into ice water to stop cooking.

4. 4

   Remove chives from ice water, squeezing out excess water, and drain on paper towels.

5. 5

   Chop chives and in a blender puree with oil until smooth.

6. 6

   Transfer chive oil to a bowl.

7. 7

   Chill oil, covered, at least 8 hours and up to 1 day.

8. 8

   Pour oil through a fine sieve into a small bowl, pressing hard on solids.

9. 9

   Thinly slice onions and in a 5-quart heavy kettle combine with broth and wine.

10. 10

    Bring mixture to a boil and skim foam.

11. 11

    Add thyme and simmer, uncovered, until onions are very tender, 45 to 50 minutes.

12. 12

    Cool mixture 10 minutes.

13. 13

    In a blender puree mixture in batches with butter until smooth (use caution when blending hot liquids), transferring to a bowl.

14. 14

    In kettle stir together puree, sugar, vinegar, pepper, and salt to taste and heat over moderate heat, stirring, until heated through.

15. 15

    Soup may be made 2 days ahead and cooled, uncovered, before chilling, covered.

16. 16

    Reheat soup before serving.

17. 17

    With a vegetable peeler shave enough thin slices from Parmigiano-Reggiano to measure about 1/2 cup.

18. 18

    Serve soup drizzled with chive oil and topped with Parmigiano-Reggiano.

* Per serving · 4 servings · Values may vary.