In a large mixing bowl, add the ground beef, egg, almond flour, minced garlic, and all the seasonings. Using your hands or a spoon, gently mix everything together until just combined. Be careful not to overmix, as this can make the patties dense and tough. You’re aiming for a mixture that holds together well but still feels soft and slightly loose.
Divide the mixture into equal portions and shape them into patties using your hands. Press them gently into round or oval shapes, about the size of your palm, making sure they are even in thickness so they cook uniformly. Avoid packing them too tightly—keeping them slightly soft will help them stay tender after slow cooking.
Heat a skillet over medium heat and add a small amount of oil. Once the pan is hot, place the patties in and sear them for about 1–2 minutes on each side until a light golden-brown crust forms. This step enhances the flavor by locking in juices and adding a rich, savory outer layer. Remove the patties carefully and set them aside.
In your slow cooker, spread the sliced onions and mushrooms evenly across the bottom. This creates a flavorful base layer that not only prevents the patties from sticking but also allows the vegetables to soak up all the delicious juices as they cook.
Place the seared patties on top of the onions and mushrooms in a single layer. Make sure they are not stacked on top of each other so that each patty cooks evenly and absorbs the flavors from the sauce.
Pour the beef broth and Worcestershire sauce evenly over the patties, ensuring all pieces are lightly coated. The liquid will slowly infuse into the meat and vegetables, creating a rich, savory gravy as it cooks.
Cover the slow cooker with the lid and set it to cook on low for 6–7 hours or on high for 3–4 hours. During this time, the patties will become tender and juicy, and the flavors will deepen beautifully. Avoid opening the lid too often, as this releases heat and can extend cooking time.
Once cooking is complete, sprinkle xanthan gum evenly into the slow cooker while gently stirring the sauce. Continue stirring until the gravy thickens to a smooth, glossy consistency. Let it sit for a few minutes to fully develop before serving, ensuring the sauce coats the patties perfectly.
