Salisbury Steak Meatballs with Mushroom Gravy

Ingredients

• 1.3 pounds ground beef
• 4 tbsp breadcrumbs
• ½ tsp garlic powder
• ½ tsp dried onion
• 1 tsp salt
• 1 tsp black pepper
• 1 egg
• 2 tsp Worcestershire sauce
• 1 tbsp ketchup
• 2 tbsp olive oil (divided)
• 2 tbsp unsalted butter
• 9 ounces mushrooms (thinly sliced)
• 2 yellow onions (thinly sliced)
• 4 garlic cloves (minced)
• 1 tsp dried oregano
• 3 tbsp all-purpose flour
• 2 cups beef broth
• 2 tsp mustard
• 1 tbsp Worcestershire sauce
• 1 tbsp low sodium soy sauce
• 2 tbsp ketchup
• chopped parsley (for serving)