Place the almonds into a food processor and blend until ground as fine as possible.
Add 50ml/2fl oz of the water and blend to a paste.
Add the bread and garlic and blend again.
With the blender motor running, gradually add the remaining the water.
With the motor still running, gradually add the olive oil.
Add the sherry vinegar and season, to taste, with salt and freshly ground black pepper.
To serve, divide the soup among four bowls and sprinkle a few raisins over each.