Step 1

1 In a large pot over medium-low heat, heat the oil until shimmering

Step 2

2 Add the onion, garlic, salt and pepper and cook, stirring, until just tender, about 2 minutes

Step 3

3 Add the zucchini and broth, increase the heat to high and bring to a boil

Step 4

4 Reduce the heat to medium-low, cover and simmer, stirring occasionally, until the zucchini is very soft, about 10 minutes

Step 5

5 Stir in the beans, tarragon and lemon zest, and remove from the heat

Step 6

6 Let the soup cool completely, then add the yogurt and, using an immersion blender (or a regular blender), puree until smooth

Step 7

7 Taste, and season with additional salt, if desired

Step 8

8 Transfer to a lidded container and refrigerate for at least 2 hours, or until thoroughly chilled

Step 9

9 When ready to serve, ladle the soup into individual bowls and garnish each with a few tarragon leaves