Soak onions in hot water until soft. Meanwhile, mix ground beef with baby food and beef broth. Using 1/4 cup of the meat mixture for each patty, flatten to 1/4-inch thickness and fry quickly in 1 tablespoon of oil per patty on a hot griddle. Make 3 or 4 holes in the patties while frying. Cut hot dog buns in half. Cut off rounded ends. Fry 1 teaspoon of onions under each patty as you turn to fry the second side. Slip each patty onto the cut bun with 2 dill pickle chips and mustard.