Mash Topped Beef & Guinness Pie

1. 2 carrots
2. 1 onion
3. 3 celery
4. 2 tsp dried rosemary
5. 2 tsp dried thyme
6. 5 cloves garlic
7. 50 g plain flour
8. 500 ml guinness
9. 200 ml beef stock
10. 1 tbsp soft brown sugar
11. 800 g diced beef
12. 2 tbsp balsamic vinegar

Mash topping

1. 500 g floury potatoes
2. 80 ml milk
3. 50 g butter