To prepare soup: Toast cumin in a small skillet over low heat, stirring, until just fragrant, 1 to 2 minutes.

Combine tomatoes, onion, 2 tablespoons cilantro and chipotle in a blender or food processor. Puree until smooth. Transfer to a large bowl. Add the toasted cumin, corn, ice water, lime juice and salt; stir to combine. Refrigerate until chilled, about 1 hour or until ready to serve.

To prepare cilantro yogurt: Puree yogurt and the remaining 1/4 cup cilantro in a blender or food processor until smooth. Refrigerate until ready to serve (it will thicken slightly as it stands).

To serve, divide the soup among 4 bowls and garnish each with a generous swirl of cilantro yogurt.

Notes: Chipotle chiles in adobo sauce are smoked jalapenos packed in a flavorful sauce. Look for the small cans with the Mexican foods in large supermarkets. Once opened, they'll keep up to 2 weeks in the refrigerator or 6 months in the freezer.

To remove corn from the cob: Stand an uncooked ear of corn on its stem end in a shallow bowl and slice the kernels off with a sharp, thin-bladed knife. This technique produces whole kernels that are good for adding to salads and salsas. If you want to use the corn kernels for soups, fritters or puddings, you can add another step to the process. After cutting the kernels off, reverse the knife and, using the dull side, press it down the length of the ear to push out the rest of the corn and its milk.

MAKE AHEAD TIP: Refrigerate the soup and cilantro yogurt in separate containers for up to 1 day.