Slow Cooker Salisbury Steak Meatballs

Ingredients

• 680 g ground beef (80/20 for flavor)
• 1/2 cup breadcrumbs (plain)
• 1/4 cup milk
• 1 large egg
• 1 tbsp Worcestershire sauce
• 1/2 tsp garlic powder
• 1/2 tsp onion powder
• 1/2 tsp salt
• 1/4 tsp black pepper
• 1 tbsp olive oil (for browning)
• 1 tbsp unsalted butter
• 1 medium yellow onion (sliced thin)
• 2 cloves garlic (minced)
• 225 g mushrooms (sliced, cremini or button)
• 2 tbsp all-purpose flour
• 2 cups beef broth (low sodium)
• 1 tbsp ketchup
• 1/4 tsp dried thyme
• Salt and pepper to taste
• Fresh parsley (chopped, for garnish)