Cook elbow macaroni until slightly al dente; drain and toss with oil. Spread macaroni on a baking sheet to cool. In large bowl, whisk together sour cream and mustard. Add macaroni; fold together until macaroni is coated with cream cheese mixture. Refrigerate, covered.
For each serving, to order, in small saucepan, heat 3/4 cup heavy cream over medium heat. Add 1/4 cup Cheddar cheese and 1 tablespoon Parmesan cheese; stir until cheese is melted. Add 2 cups macaroni and 2 tablespoons bacon; stir until macaroni is hot. Add 1 tablespoon chives and 1 tablespoon parsley; season with salt and pepper. Transfer to serving bowl; sprinkle with 1/4 cup breadcrumbs.
Recipe by Chef Eduardo Martinez, Market Restaurant, St. Helena, Calif.