Cook 1 pound asparagus (trimmed, peeled and cut into 1-inch pieces) in salted boiling water until crisp-tender, 2 to 3 minutes. Remove with a slotted spoon and transfer to ice water to cool; drain. Add 1 pound quartered baby potatoes to the boiling water and cook until tender, 8 to 10 minutes, then drain. Whisk 1/2 cup creme fraiche, 1/4 cup each chopped chervil and chives and 2 tablespoons each olive oil, white wine vinegar and chopped dill in a large bowl. Add the asparagus and potatoes; season with salt and pepper and toss. Refrigerate.