Combine ground turkey, half of the chopped onion, half of the Worcestershire sauce, the egg, breadcrumbs, salt, and garlic powder in a bowl
Form 5-6 patties and place them in a skillet with heated olive oil
Cook on medium heat for 4-5 minutes
Flip the patties and cook under a lid on low heat for another 5 minutes
Remove the patties to a plate
Add mushrooms and the remaining onion to the skillet
Sauté over medium heat for 5 minutes, stirring occasionally, then remove to a plate
Melt butter in the skillet and add flour
Cook, stirring, for 3 minutes
Gradually pour in the beef broth, stirring to dissolve any lumps
Heat until the sauce thickens
Return the patties to the skillet, placing them in the sauce
Top with the sautéed mushrooms and onions
Cover and cook on low heat for 15 minutes
Let cool slightly before serving