In a large bowl, combine the ground turkey, egg, breadcrumbs, diced onion, ketchup, garlic salt, ground mustard, and a pinch of salt and pepper. Mix gently with your hands until just combined—avoid overworking the mixture, as this will make the patties tough and dense. Divide the mixture into 6-7 equal portions and shape each into a patty about 3/4-inch thick. I like to make a slight indent in the center of each patty with my thumb; this helps them cook evenly and prevents them from puffing up in the pan.

Heat 1 tablespoon of olive oil in a large skillet over medium-high heat until shimmering. Once hot, carefully place the turkey patties in the pan, working in batches if needed to avoid overcrowding. Let them cook undisturbed for 4-5 minutes until the bottoms develop a golden-brown crust, then flip and cook for another 3-4 minutes on the second side until browned (they don't need to be cooked through at this point). Transfer the browned patties to a clean plate and set aside.

Add the remaining 1 tablespoon of olive oil to the same skillet over medium-high heat. Add the sliced mushrooms and sauté for 3-4 minutes, stirring occasionally, until they begin to release their moisture and turn golden. The mushrooms will add deep umami flavor to the gravy, so don't skip this browning step. Transfer the mushrooms to the plate with the patties.

Reduce the heat to medium and add the butter to the same skillet, allowing it to melt completely. Sprinkle the flour over the melted butter and whisk constantly for 1-2 minutes to create a smooth paste (called a roux). This toasted flour base will thicken your gravy while adding a subtle savory depth. Gradually pour in the beef broth while whisking continuously to prevent lumps from forming.

Increase the heat to medium-high and bring the gravy to a gentle boil, stirring occasionally, until it thickens slightly and coats the back of a spoon (about 2-3 minutes). Stir in the Worcestershire sauce and onion powder, then return the turkey patties and sautéed mushrooms from Step 3 to the pan. Reduce the heat to low, cover the skillet, and simmer gently for 10 minutes to allow the patties to finish cooking through and the flavors to meld together. The gravy should coat the patties beautifully and the turkey should reach an internal temperature of 165°F.

Transfer the turkey patties to a serving plate and spoon the rich mushroom and onion gravy generously over the top. Serve immediately alongside creamy mashed potatoes or your favorite side dish to soak up the delicious sauce. I prefer using quality Kerrygold butter in the gravy—the rich, golden color and slightly higher fat content really elevates the final dish compared to standard butter.