French Dip

Despite the name, this American specialty is completely unknown in France itself, the name seeming to refer to the style of bread, rather than an alleged French origin.
Two Los Angeles restaurants have claimed to be the birthplace of the French dip sandwich: Cole's Pacific Electric Buffet and Philippe the Original. Philippe's website describes the dish as a "specialty of the house", and the words "Home of the Original French Dip Sandwich" are present in the restaurant's logo. At both of these restaurants, the roll is dipped in the hot beef juices before the sandwich is assembled, and is served "wet". The sandwich can also be requested "double dipped" at either establishment. Philippe's own brand of spicy mustard is traditionally used by patrons to complement the sandwich.
This controversy over who originated the sandwich remains unresolved. Both restaurants were established in 1908. However, Cole's claims to have originated the sandwich shortly after the restaurant opened in 1908, while Philippe's claims that owner Philippe Mathieu invented it in 1918.
The following is from an article at https://www.thrillist.com/, written by journalist Jackson Landers:
The actual closest that we can get to the horse's mouth is a 1951 LA Times interview with Mathieu. The article was written on the occasion of Philippe's relocating to make way for the Hollywood Freeway.
“One day a police officer asked me if I would mind splitting one of these large loaves of French bread and filling it with 'some of the delicious roast pork,'” said Mathieu. “I was not too busy, so I said, 'Sure.' Then he asked me to 'please cut it in half. I've got a friend outside who can eat it.' Then he asked for some pickles, onions and olives.”
The sandwich was born and awaited its dip.
"Then we started making French-roll sandwiches for those who had smaller appetites," Mathieu said. "One day a customer saw some gravy in the bottom of a large pan of roast meat. He asked me if I would mind dipping one side of the French roll in that gravy. I did, and right away five or six others wanted the same."
French Dip
Long hoagie rolls, split lengthwise
Rare roast beef, sliced thin
au jus (made when you roast your beef)
horseradish or Horseradish Cream
Provolone cheese, thinly sliced (optional)
Heat the au jus until very hot. If using cheese, place cheese on the both sides of the split rolls and melt under the broiler. Otherwise, toast the bread. Warm the beef in the au jus briefly (you don't want to cook the beef, just warm it quickly). Place beef slices on top of the cheese.
Serve with horseradish or Horseradish Cream and au jus for dipping on the side.