Savory Bistro Hamburger Steak

Ingredients

• 2 tsp mustard
• 1 cup beef broth
• 1/4 tsp black pepper
• 1/2 tsp sea salt
• 2 tsp garlic powder
• 1 tbsp chopped parsley, for topping
• 2 tsp arrowroot starch
• 1 tbsp coconut aminos
• 2 tsp apple cider vinegar
• 1 tsp dried thyme
• 2 cups mushrooms, sliced
• 1 tsp sea salt
• 1 lb ground beef
• 3 tbsp avocado oil
• 1 large yellow onion, thinly sliced