Put the garlic in a food processor or blender with the ground almonds and breadcrumbs .
Measure 550ml (20fl oz/ 2 ½ cups) cold water into a jug. Add a little of the water to the breadcrumb mixture and process to form a paste. With the motor running, gradually pour in the oil, vinegar and remaining water.
Transfer to a bowl, season with salt and pepper and chill for at least 1 hour. Whisk the soup and adjust the seasoning. Halve the grapes and stir into the soup with the coriander. Serve in chilled bowls.