Place potato pieces into a large saucepan, and cover with salted water. Bring to a boil, turn the heat down, and simmer for 5 minutes approximately

Add the sweet potato, and cook about 8-10 minutes more or until potatoes are tender but still firm enough to hold their shape.

Once the potatoes are tender, add corn kernels; cook another 30 seconds. Drain through a colander.

Fill the saucepan with cold water, and drop vegetables into water. Cool for 5 minutes, and drain.

In a large bowl, whisk together mustard, lime juice, coriander, and garlic. Slowly whisk in oil. Mix in salt and black pepper.

Add cooled potatoes, to dressing along with cucumber, and red onion. Toss well. Serve at room temperature or chilled. Toss the peanuts in just before serving.