Heat oil in a large Dutch oven over medium-high heat. Add leek, and sauté 5 minutes. Reduce heat to medium; add potato, 1/2 cup parsley, thyme, salt, and bay leaf. Cook 15 minutes, stirring occasionally. Add water, and bring to a boil. Cover, reduce heat, and simmer 20 minutes. Discard bay leaf.
Combine 2 cups potato mixture and tofu in a blender or food processor, and process until smooth. Return the puréed potato mixture to pan. Stir in 1/2 cup parsley and pepper. Cook for 5 minutes or until thoroughly heated.