Bring a large pot of water to boil. Cook pasta 7 to 8 minutes or until tender but still firm to the bite. Meanwhile, whisk milk and cornstarch together in a non-reactive saucepan. Slowly bring this mixture to a simmer, whisking constantly over medium heat. Stir in 3/4 of the cheese into sauce and reduce heat to low. Stir constantly until cheese melts, about 1 minute. Add remaining cheese, remove pan from heat and let cheese melt by the heat of the sauce. Season with Worcester sauce, salt, and cayenne pepper. Drain and dry pasta and transfer to a serving dish. Toss hot pasta with most of the ham, spoon sauce over hot pasta and serve immediately. Garnish with remaining ham.