Beef Wellington
The tenderloin is brushed with Dijon mustard, wrapped in finely chopped sauteed mushrooms and prosciutto, then wrapped again in puff pastry. The mushrooms cook until nothing pools in the pan, and they and the beef must be cold through before wrapping, or the pastry base turns soggy. It comes out when a thermometer pushed in from the side reads 63 degrees at the center of the meat, whatever the color of the crust.