Meatballs and Gravy

Ingredients

• low-calorie cooking spray
• 12 reduced-fat beef meatballs
• 1 medium red onion, (peeled and diced)
• 4 mushrooms, (diced)
• 1 tsp garlic granules
• 1/2 tsp dried rosemary
• 1/2 tsp dried thyme
• 2 tbsp balsamic vinegar
• 1 tbsp Henderson's relish or Worcestershire sauce
• 1 tbsp tomato puree
• 400 ml boiling water
• 1 beef stock cube
• 1 tbsp cornflour
• 1 tbsp cold water
• salt and freshly ground black pepper, (to taste)