Beef soup base (cantonese style)

Ingredients:
2kg beef bones
60 g butter
6L water
9 tbsp tomato paste
1.5 carrot cut into wedges
4 stalks celery cut into sections
2 tomatoes cut into wedges
3 onions cut into wedges
12 cloves garlic chopped finely
4 bay leagves
1.5 tbsp mixed herbs
some peppercorns

Precedures:
Bring water to boil over high heat. Wash beef bones. Chop into pieces.
heat up wok, add butter and melt it over low hear. Add beef bones. Stir fry over medium heat till half done.
Add celery, carrot, tomato and chopped garlic. Stir fry till just tender. Add peppercorns and tomato paste. Stir fry till brownish golden color.
Preheat oven to 210 oc. Put all stir fried ingredients into oven and bake for 30 to 45 mins (Stir and turn ingredients every now and then). Remove from oven.
Put baked ingredients into boiling water. Add mixed herbs. Simmer over low heat for another 3 hours ( while simmering, remover bubbles on top with small spoon) Stain off ingredients. Soup base is done.