In the United States, both mac & cheese and grilled cheese sandwiches have actually been a part of McDonald's menu lore for quite some time -- long enough for us to do taste tests of both items in 2015. The verdict on the grilled cheese, a "secret menu" item which really just amounts to two McDonald's hamburger buns and a slice of American cheese, was a resounding "No." Later that year, while the chain's Cleveland locations tested its mac 'n' cheese in Happy Meals, an editor with a niece and nephew described it as "an adequate Happy Meal option for kids who don't like meat."
McDonald's Hong Kong's grilled cheese toasties sound way tastier than that, but sadly we can expect these to arrive in the United States right around the same time McDonald's Japan's deep-fried mac 'n' croquette burgers do, aka never. An Asian vacation looks better and better by the minute, y'all.