Start the sauce beurre blanc: place the shallots, pepper, salt, vinegar, and water in a small saucepan. Simmer for 25 to 30 minutes, until the mixture reduces. Push the mixture though a fine sieve. There should be about a half tablespoon of puree produced.
Remove the salmon pieces from the saucepan. Drain the sauerkraut and divide between the serving plates. Arrange the potatoes and salmon pieces on the sauerkraut. Spoon the sauce over the salmon. Serve immediately.