A milk steak is a block of cheese. Cheese being made from milk and is sold in a block shape. Much like a steak.and boiled over
hard could possibly mean melted because of Charlie's dyslexia and inability to understand and articulate the right words in general.
On an episode of it's always
Sunny in Philadelphia Charlie mistakenly calls block of cheese and milk steak because of his nervousness while meeting the
beautiful attorney.