In a large bowl, soak bread in water for 15 minutes. Squeeze bread and place in a small bowl (there should be about 1 cup of bread); set aside.
In a blender, combine the lemon juice, potatoes, garlic and salt; cover and process until smooth. Add bread; cover and process until blended.
While processing, gradually add oil until blended. Transfer to a serving bowl; sprinkle with nuts if desired. Serve with pita ships or crackers. Store in the refrigerator.