Preheat the oven to 350°F. Combine the ground beef, egg, almond meal, salt, mustard, onion powder, baking soda, cream of tartar, and 1/2 tsp. of the pepper in a mixing bowl. Mix with your hands until everything is well combined; be careful not to over mix.

Form the meat into 4 steak-shaped patties and place on a baking sheet. Bake until browned, about 18 minutes, then broil for 2 minutes to create a crust.

While the steaks are cooking, combine the broth, mushrooms, and the remaining 1/2 tsp. pepper in a small saucepan. Bring to a simmer on medium heat, then reduce the heat to medium-low and simmer until the mushrooms shrink and soften, about 15 minutes. Stir in the cream or coconut milk and reduce the heat to low. In a separate dish, mix together the starch and cold water to create a slurry. Stir the starch slurry into the broth and simmer until thickened, about 3 minutes. Add salt and pepper to taste, then plate the steaks and pour the gravy on top.