In a large bowl, mix together all of the ingredients for the dressing.
To the dressing add the potatoes, cauliflower, radishes and snap peas.
Toss the vegetable and dressing together and then place in the refridgerator to marinate for 15 minutes, tossing once more at about 10 minutes.
Place the White Fish fillets on a cutting board. Run your fingers alon the fillets to locate any pin bones. Removing them is quite a bit easier if you pull them out with a tweazers (If you use this method, make sure to wash the tweazers well before and after using).
Season the de-boned fillets with the salt and white pepper.
Lightly whisk the egg in a shallow bowl. In a seperate bowl combine the breadcrumbs and salt.
Dip the fillets in the egg and then dredge in the breadcrumb mixture.
In a large fry pan at medium-high heat add the butter and fry the fillets until they are golden brown.
Drain off the extra fat by placing the fillets on a paper towel. This will also keep them crispy.
Serve the fried fillets on top of a decent portion of the potato salad.