To make the dressing, in a blender or food processor, combine the tofu, lemon zest and juice, mustard, anchovy paste, garlic, salt, and pepper. Process until smooth. With the motor running, slowly add the olive oil. Cover and refrigerate until needed.
Put the potatoes in a saucepan, add water to cover and bring to a boil over high heat. Reduce the heat to medium and cook uncovered, until the potatoes are tender, about 15 to 20 minutes. Drain and let stand until just cool enough to handle. Cut each potato in half — or quarters, if the potatoes are large. In a bowl, toss the potatoes gently with half of the dressing. Set aside and keep warm.
Season the scallops with the salt and black pepper. In a large frying pan, heat the olive oil over medium-high heat. Place the scallops in the hot pan and sear on one side until golden, about 1 minute. Turn and cook on the other side until the scallops begin to turn opaque at the center, about 1 to 2 minutes longer. Remove from the heat.
To serve, toss the greens with the remaining dressing and divide among individual plates. Scatter the potatoes and scallops over the greens. Sprinkle with the chives and cracked pepper. Serve immediately.