Place tofu between paper towels. Top with a plate weighted with an unopened can of food. Let stand 30 minutes to press out as much liquid as possible, replacing paper towels once during pressing.
Cut tofu into ½-inch cubes. In a large bowl toss together tofu, potatoes, celery, onion, and radishes.
In a small food processor or blender combine cashews, nutritional yeast, and mustard. Process until smooth, gradually adding plant milk until dressing is the consistency of ranch dressing.