Heat a 10-inch sauté pan over medium-high heat, and add the olive oil to the pan; add the pumpernickel cubes to the pan and toss to coat with the oil. Season with the white pepper.
Continue to cook and toss the bread until all the oil has been absorbed. Place the pan in the oven and continue to cook, tossing occasionally, until the bread is crisp, about 10-12 minutes. Remove the bread from the oven and allow to cool before using.
Make the vinaigrette by combining the shallots, garlic, mustard, honey, capers, lemon juice, champagne vinegar, dill and parsley in a non-reactive mixing bowl. Whisk to combine. Season with the ¼ tsp of black pepper. While whisking, add the extra-virgin olive oil in thin, steady stream until the vinaigrette is well combined and partially emulsified. Set the vinaigrette aside while you prepare the salad.
On 4 large, chilled plates, place three slices of the salmon along the edges of the plates. In a large, non-reactive bowl, place the watercress and red onion, and add about ½ cup of the vinaigrette to the salad. Toss lightly to combine. Divide the salad among the 4 plates, and divide the croutons among the plates.