In a large bowl, mix the venison and ground beef.
Heat a large cast iron skillet over high heat. Form the meat mixture into 1/4-inch thick square patties on a piece of parchment paper. Flip the parchment over into the hot skillet, allowing the meat to retain its shape. Poke holes with a fork or the end of a wooden spoon to keep the shape of the patties.
Allow the patties to cook for about 1 minute or until the bottoms of the patties are done and then turn them over and cook for another minute. If you are adding cheese, once you flip the burger, place a slice of cheese over the patty and continue cooking until the cheese is melted.
If you are using dried minced onions, add ½ cup hot water to the dried onions and set aside. If you are using fresh onions, add ⅓ of the onions to the side of the skillet without the patties and pour about ¼ cup of water over the top of the onions to allow them to steam. After the steam dissipates, place the tops and bottoms of the buns over the onions for one minute.
If using dried onions, toast the buns in the skillet with the meat. Remove the buns to a plate with the bottom bun cut side up. Put a patty on each bottom bun. Then add a teaspoon of onions, a squirt of mustard, and 2 pickles. Put the top bun on each burger. Repeat with the remaining ingredients.