Veggie gravy - Good Food Middle East

Ingredients

• 1 onion, chopped
• 2 carrots, finely chopped (about 200g)
• 2 celery sticks, finely chopped (about 200g)
• 2 bay leaves
• 1 large thyme sprig
• large knob of butter (or 2 tbsp olive oil)
• 1 tbsp golden caster sugar
• 2 tbsp plain flour
• 2 tsp Marmite (optional)
• 1 tbsp tomato purée
• 2 tbsp balsamic vinegar
• 1l vegetable stock