When I make these burgers for a weeknight meal I use ground turkey because we don't eat red meat much in our house. Although, when I'm having company or doing a summer barbecue for lots of friends sometimes I do both versions. These are VERY family friendly. Picky eaters don't ever know what's hiding in a delicious juicy burger. Trust me. This is a winner.
Also, I'm a huge fan of the BBQ (even in the winter), but if this is not an option for you, feel free to use an indoor grill pan or to broil them in your oven.
3 pounds of ground chopped meat (if using beef- mix 1.5 pounds lean with 1.5 pounds regular ground beef)
1 whole egg
¾ teaspoon kosher salt
¼ teaspoon black pepper
2 clove fresh garlic, chopped
1/3 cup duck sauce (you can use maple syrup if you prefer a more natural sweetener)
Take a large sauté pan and heat up 2 tablespoons of your olive oil under medium-high heat. When the oil is hot (you will see ripples running through it) add your onion and fennel with ¼ teaspoon of the kosher salt. Allow the onion and fennel to cook for 5 minutes, and then add your spinach and 1 clove of the chopped garlic and cook for an additional 5 minutes. (All the spinach should be wilted.) Allow the mixture to cool completely.
In a separate mixing bowl combine the beef, egg, remaining 1/2 teaspoon of salt, pepper and garlic. When it is fully combined, add your spinach mixture and mix it in thoroughly. Form hamburger patties (sliders or regular sized) and place aside into a tray (in the fridge) until you are ready for grilling. Alternatively your can wrap them individually in plastic wrap and store in a zippered bag in the freezer.
When you are ready to grill, preheat your BBQ to high for 15 minutes. Clean your grill grates well with a metal BBQ brush. Lower your grill to medium-high and cook your burgers for 8 minutes per side. After you flip your burger at the first 8 minute mark, take your duck sauce and a basting brush and brush each burger generously with the duck sauce.
Note: A good grilling trick to learn is not to force your meat when you want to flip it. If it is sticking to the grill it is probably because it is not ready to be flipped. Your meat will release from the grill when it is ready to turn. If you go to flip it and it is stuck to the grates - instead of forcing it wait 30 seconds and then try to flip it again.
You can form and freeze your burgers and store up to 2 months in the freezer. Wrap each patty in plastic wrap and store the wrapped patties in a labeled zippered freezer bag.
If you are preparing it fresh, it needs to be mixed and formed the day of serving. After the vegetables are mixed into the meat, it only lasts 1 day in the fridge. As a general rule, I don't keep chopped meat in the fridge longer than 1 day as it begins to turn pretty quickly.