Preheat the oven to 400 degrees F. Butter and flour 1 large souffle dish or 4 to 6 individual ones with an 8 to 12 ounce capacity.
Heat the milk in a saucepan over low heat. Melt the butter in a medium saucepan over medium heat, then add the flour, whisking until smooth and creamy. Cook about 3 minutes, until the mixture turns straw colored. Whisking, pour in the hot milk, and whisk constantly over medium heat until the mixture thickens, about 1 to 2 minutes.
Remove from the heat and stir in the cheeses, 4 egg yolks, corn, and mustard. Season with salt and pepper, to taste. Set aside to cool 5 minutes. Whip the egg whites until soft peaks form, and then fold into the souffle mixture in thirds with a rubber spatula.
Pour the mixture into the souffle dish or dishes, and then place them in a roasting pan. Pour hot water into the pan until it comes halfway up the sides of the dish. Bake 25 to 35 minutes for individual souffles, 35 to 45 minutes for large ones, until risen and slightly firmed. Serve immediately or let the souffles cool in the dish, then turn out, cover, and refrigerate. (The dish can be made up to this point up to 24 hours in advance.)
If made ahead of time: to serve, arrange the turned out souffles in a baking dish, poke a hole in the top and pour a little heavy cream inside, then drizzle a little heavy cream over the top of each souffle, and bake at 400 degrees until hot and bubbly, about 10 minutes.
Notes about the recipe: When I agreed to go to England to revitalize the flagging cuisine at Stapleford Park, a hotel owned by our friend Bob Payton, I had no idea what to expect. But having heard all the jokes about English cooking, I did wonder if they would like my food. As soon as I arrived in Melton Mowbray, a town dedicated to making strong, creamy Stilton cheese, we knew everything would be fine. The entire town of Melton Mowbray smells of Stilton, especially the fine cheeses of the firm of Tuxford & Tebbutt that may be what inspired me to cook with it so often, creating new lunch and supper dishes like this one. The richness of the local agricultural traditions quickly impressed me: the milk, butter, eggs, lamb, and vegetables were just as perfect and flavorful as the Stilton cheese. According to legend, Stilton was invented by a Mrs. Paulet in the 1700s. The cheese must be cylindrical, must ripen without ever being pressed, and must form its own coat or crust. Red Leicester, a vibrant orange, crumbly aged cheddar-style cheese, furthered our education in the best products of English kitchens. More words and warnings have been devoted to the making of souffles than any other cooking subject, but this one doesn't rise perilously high. An airy egg batter, fresh milk, and butter, savory cheese and, in this case, sweet corn kernels and a dash of mustard produce irresistible results. If you want to make your souffles even more luxurious, follow the reheating instructions by pouring a dollop of heavy cream inside each one for the last 10 minutes of cooking.