Roughly chop the celery, bell peppers, cucumbers, bread, chile, and garlic. Place these in a large bowl along with the sugar, walnuts, spinach, basil, parsley, vinegar, oil, yogurt, 1 1/2 cups of the water, half the ice cubes, the salt and some white pepper. Working in batches, blitz the soup in a blender until smooth, pouring each batch into a bowl and stirring to combine at the end. If desired, add as much of the remaining 1/2 cup water, a little at a time, to get your preferred consistency. Taste the soup and adjust the ingredients accordingly. If desired, pour a little of the soup back into the blender and add the remaining ice and pulse once or twice, just to crush it a little. Stir this into the rest of the gazpacho.