In every UA flight with international first class, there is a printout taped up on the galley with everyone's special requests. One FA puts on a chef's hat (as I am sure you have noticed), defrosts the raw fish or meat and cuts up the fresh vegetables that he/she has sourced from the local farmers' market, and then cooks each dish according to the passengers' specifications. However, these requests have to be submitted at least 24 hours in advance. Note that UA disclaims all responsibility for steaks ordered medium-well or well-done---read the CoC.