Step 1

Whisk vinegar, lime juice, 1 cup yogurt, and ½ cup oil in a large bowl until smooth. Add bread, cucumber, bell pepper, tomatillos, scallions, jalapeños, garlic, and ¾ tsp. salt and toss to coat (make sure bread is well coated so it can soak up as much flavor as possible). Cover and chill at least 4 hours.

Step 2

Working in batches, purée bread and vegetable mixture in a blender until very smooth; transfer to a large bowl and season gazpacho with salt.

Step 3

Whisk remaining ½ cup yogurt in a small bowl, thinning with water a tablespoonful at a time, until the consistency of heavy cream; season with salt.

Step 4

Serve soup in chilled bowls. Drizzle with thinned yogurt and more oil and sprinkle with piment d’Espelette.

Step 5

DO AHEAD: Gazpacho can be made 1 day ahead; cover and chill. Mix well before serving.