New Wave Macaroni Salad

Cook bacon in a large skillet until crisp. Drain bacon on paper towels, cool and chop. Heat a large saucepan of lightly salted water to a boil. Add macaroni and cook until just tender, stirring frequently. Drain macaroni well and cool under cold running water. Drain again. Whisk together mayonnaise, buttermilk, lemon juice, Dijon and sugar in a large bowl. Add macaroni, bacon, mushrooms and peas. Toss well to coat. Cover and refrigerate until ready to serve.