3 fennel sour dressing Recipes

sour cream, olive oil, divided, prepared horseradish, chopped fresh dill, white wine vinegar, divided, arugula, sliced fennel bulb, sliced red onion, smoked trout or smoked whitefish, coarsely flaked

yukon gold or boiling potatoes (about 3), peeled and cut into eighths, frozen peas, skinless salmon fillets, fennel bulb, fronds reserved, bulb sliced into matchstick strips, sour cream, mayonnaise, chopped fresh chives or scallion tops, olive oil, lemon juice, salt, fresh-ground black pepper, watercress (about 3/4 lb), tough stems removed (about 1 1/2 quarts)