Preheat oven to 350°. Put piecrust in a 9-inch pie plate, or removable bottom tart pan. Spread 1 cup Swiss cheese over the bottom of the crust, top with bacon, mushrooms, and chives, then add second cup of cheese. Beat together the eggs, mayonnaise, cream and seasonings. Pour over ingredients in the pie crust. Bake one hour or until set. A table knife inserted in the center will come out clean. Let quiche cool 10 minutes before slicing and serving.