Method for a mortar and pestle: with a mortar and pestle, mash the ingredients together, in the following order: First the salt and garlic cloves, then the green peppers and onion. Add 1 slice of the bread, so that the mixture doesn't spatter. Right away, while mixing by hand, add the olive oil in steady stream, the sherry vinegar, and finally the second slice of bread and the tomatoes. Pound and crush the gazpacho mixture, extremely well. To finish, add the cold water. Chill for 1-2 hours. Adjust salt and seasoning, if needed and serve cold. The resulting Gazpacho should have a chunky texture.
Method for a blender: peel and de-seed the tomatoes and set aside. In a blender, pulse the garlic cloves and salt, for a few seconds. Add the green peppers and onion piece and blend to break down. Add a one slice of bread and pulse. Add the tomatoes and the second slice of bread and with the blender still running, stream in the olive oil until blended and smooth. To finish add the sherry vinegar at the end. Pour into a large bowl or soup terrine and the cold water. Stir well. Chill for one to two hours and adjust salt and seasoning, if needed. Serve cold. The resulting Gazpacho should have a smooth texture.