The secret of making good soup is having good broth. Start by putting all the stock ingredients in a large pot. This means adding beef bones, onion, leek, ginger, garlic, star anise, cinnamon and salt in the pot. Add water and bring to boil.
Simmer this for 2-3 hours on low heat. When the broth has been reduced in half, just enough to make 2 bowls of soup, remove from the stove. Strain and discard the bones and vegetables. The broth should be clear without any solid residues. Put the broth back into the pot and keep it on low-heat.
Cut raw beef into thin slices. Chop green onions. Shred the zucchini to make zucchini noodles using a spiralizer. Slice mushroom (if using).
If you use mushroom in this recipe, add mushroom back into the broth pot and cook for a few minutes on low heat.
You can cook the zucchini noodles by simply dipping it in the boiling broth for 1 minute using a slotted spoon. Remove zoodles and place in a bowl. You can do the same for sliced beef to cook it. Do not overcook the beef or it will become too tough and chewy to eat.
In a bowl with cooked zucchini noodles at the bottom, add sliced beef on top along with green onions, bean sprout and mushroom. Pour the boiling broth into the bowl and serve. You can add a few slices of jalapenos for spiciness.