Slow Cooker Salisbury Steak Meatballs - Petite Panini

Ingredients

• 680 g ground beef
• 0.5 cup breadcrumbs
• 0.25 cup milk
• 1 large egg
• 1 tbsp Worcestershire sauce
• 0.5 tsp garlic powder
• 0.5 tsp onion powder
• 0.5 tsp salt
• 0.25 tsp black pepper
• 1 tbsp olive oil
• 1 tbsp unsalted butter
• 1 medium yellow onion
• 2 cloves garlic
• 225 g mushrooms
• 2 tbsp all-purpose flour
• 2 cups beef broth
• 1 tbsp ketchup
• 0.25 tsp dried thyme
• Salt and pepper to taste
• Fresh parsley