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.