Macarons
Good ones abound, but Pierre Hermes is my ultimate.
They cannot make a good macaron in the U.S.
U.S. style (everything): sugar. This applies to Ladurée in Manhattan as well (who makes a perfectly respectable macaron in Paris). After biting into each of the three I bought, disappointment growing each time, I actually threw away the box of remains. This is not something I would ever do lightly.
French style: distinct flavors that make mini explosions of joy in your mouth. My friend brought me this box on the plane from France, so I had the opportunity to test them again at home in Boston. Yup, still spectacular bundles of wonder.