Westerners roast their meat bones and vegetables in the oven before dumping them in a pot of water to make broth. Asians don’t do the roasting bit. Except, perhaps, for the South Asian tandoor, traditionally, there are no ovens in Asia. Ovens in Asian kitchens are modern additions during the last couple of decades. But long before that, the Vietnamese have been charring their onions, garlic, and ginger in an open flame before adding them to meat bones to make broth. Some might say it is the equivalent of roasting but charring the vegetables gives the broth a depth of flavor that roasting seems unable to impart.
I wrote all that to explain the first reason that makes Vietnamese pho different from the gamut of Asian noodle soups. The second reason is the amount of vegetables that go into every bowl of pho and the third is the variety of herbs among the greens in the pho. To make the broth for the pho, start with meat bones. Place in a pot of water, boil for ten minutes, throw out the water, and rinse the bones (this removes all the scum), fill a clean pot with water, add the bones, and boil once more.
Meanwhile, char a couple of onions, whole garlic, and a generous knob of ginger. Just place them directly on the flame (if you’re using a gas stove). Or, if you’re a neat freak, use a fish basket (see a photo of a fish basket in the chicken inasal entry). It’ll take only a couple of minutes to char the vegetables. Do not wait until they turn mushy. When the skins are charred remove them from the flame. Scrape off the blackened skins and discard. Add the vegetables to the broth. Add some peppercorns and bay leaves too. Season with fish sauce. Simmer the bones, spices, and vegetables for at least two hours until reduced.
Now, you have the broth. Make a bowl of pho bo tai. While you assemble the pho bo tai, keep the broth simmering. Place the noodles in a bowl. Add the beef, carrot, and Chinese cabbage. Pour in the simmering broth (the broth will instantly cook the beef, trust me). Top with mung bean sprouts, fried onion slices, and toasted garlic. Sprinkle the herbs on top (or serve separately) along with the onion leaves. Squeeze some lemon juice into the bowl of pho and enjoy.