Cedar baked salmon with watercress yogurt sauce

Ingredients
2 untreated cedar, shingles
4x6 ounce salmon, fillets, boneless, and, skinless
2 bunches watercress, stems removed
1/2 cup light plain yoghurt
1 tablespoon chopped fresh dill
2 tablespoons sour cream
2 tablespoons milk
1/2 teaspoon Worcestershire sauce
1/2 teaspoon Dijon mustard

Directions
Soak the cedar shingles in water for at least two hours or preferably overnight.
Preheat the oven to 425 degrees. Spray the shingles with non-stick shortening. Place two filets of the salmon one each shingle. Bake for 10 to 15 minutes until done.
Steam the watercress leaves briefly until they turn a bright green colour then spread them out on paper towels to cool. Chop the cool watercress finely and mix with the remaining ingredients. Season to taste with salt and pepper. This sauce may be served chilled or at room temperature.
Serve the baked salmon with the watercress sauce