This recipe provides detailed instructions for making rich and creamy mashed potatoes with a flavorful homemade gravy. The mashed potatoes are made with Russet or Yukon Gold potatoes, enriched with butter, heavy cream, milk, Boursin cheese, and sour cream. The gravy features a roux base with butter, garlic, thyme, Marsala and Chardonnay wines, and beef or chicken stock, finished with Worcestershire and soy sauce.