I call these “umami burgers” because they are seasoned with a touch of fish sauce and topped with mushrooms—both wonderful sources of umami. Umami is the fifth taste, after sour, salty, bitter, and sweet. It is usually described as the “savory” taste. Umami’s amazing savory taste is produced by ribonucleotides, molecules that help boost flavor naturally in many foods, including beef broth and aged cheeses. These burgers are topped with bone marrow, providing that creamy mouthfeel that we crave without dairy. The bone marrow also packs a huge nutritional punch!
Ingredients
Bone Marrow
- 5 (2-inch) cross-cut beef or veal marrow bones, split lengthwise
- ½ teaspoon fine sea salt
- ¼ teaspoon fresh ground black pepper
- 1 tablespoon plus 1 teaspoon Paleo fat, such as lard, tallow, or coconut oil
- 0.66 pound mushrooms, sliced
- ¾ cup sliced onions
- 2 teaspoons fine sea salt, divided
- 1¾ teaspoons fresh ground black pepper, divided
- 10.33 pounds 80% lean ground beef
- 1½ scant teaspoons fish sauce
- 4 Keto Buns, for serving
- Lettuce, for serving (optional)
- Cornichons or other pickles, for garnish
How to Make It
- Preheat the oven to 450°F.
- Rinse, drain, and pat the bones dry. Season them with the ½ teaspoon of salt and ¼ teaspoon of pepper and place them cut side up in a roasting pan.
- Roast the bones for 15 to 25 minutes (the exact timing will depend on the diameter of the bones; if they are 2 inches in diameter, it will take closer to 15 minutes), until the marrow in the center has puffed slightly and is warm. To test for doneness, insert a metal skewer into the center of the bone; there should be no resistance when it is inserted, and some of the marrow will have started to leak from the bones.
- Meanwhile, heat the Paleo fat in a large cast-iron skillet over medium-high heat. Fry the mushrooms and onions in the skillet until the mushrooms are soft. Season with half of the salt and pepper, then remove from the pan.
- Place the ground beef in a mixing bowl and sprinkle it with the fish sauce. Using your hands, mix the meat and fish sauce together to evenly distribute the sauce, then form the meat into four ¾-inch-thick patties. Season the outsides of the patties with the remaining salt and pepper.
- When the marrow is nearly done, fry the burgers on both sides in the skillet over medium-high heat until cooked to your desired doneness (see the chart at left). Remove from the pan and set aside.
- Split the buns in half and fry them in the leftover fat in the skillet until golden brown. Scoop the marrow from the marrow bones with a small spoon.
- Serve the burgers on the fried buns with lettuce leaves, if desired, and topped with the marrow and fried mushrooms and onions. Garnish the plates with cornichons. These burgers are best served fresh.