Milksteak is a meal enjoyed by Charlie Kelly. It was mentioned in the Season 5 episode "The Waitress is Getting Married" where Charlie wants to put it down as his favorite food in an online dating profile. It is later mentioned in the same episode as Charlie orders it in the restaurant.
Milksteak is a literal steak boiled in milk. Charlie details that he would like the milksteak "boiled over hard" and garnished with "raw" jelly beans.