For the poaching liquid:
Fish head and bones
Few stalks celery, sliced, if desired
1/2 pound carrots, peeled, sliced, if desired
1 small bunch parsley
2 cups dry white wine
Water
Salt
Black peppercorns
4 (6 to 8-ounce) center cut, skinless, salmon fillets
For the cucumber sauce:
1 English cucumber, unpeeled, roughly chopped
Fronds from 1 bunch dill (about 1 cup)
1/2 small red onion
2 large lemons, juiced
1/3 cup mayonnaise
2 tablespoons extra-virgin olive oil
1/3 cup yogurt
Salt and freshly ground black pepper
Combine first four ingredients in a blender and puree. Gradually blend in mayonnaise, oil and yogurt and then season, to taste, with salt and pepper.
Serve poached salmon with side of sauce.