Pho bo

Step 1: Put the 3 ⅓ lb beef marrow and knuckle bones in your largest pot, cover with cold water and bring to the boil over a high heat. Boil hard until grey scum rises, then tip into a colander, rinse each bone under the tap and scrub the pot clean. Common mistake: skipping this blanching. The scum and blood then cloud the broth and it never turns clear.

Step 2: Meanwhile char the 2 onions and 2 ⅞ oz fresh ginger directly over a gas flame with tongs, or cut side up under a very hot grill, turning now and then, until blackened in patches and softened at the edges. Cool slightly and rub off any loose, flaky skin.

Step 3: Toast the 5 star anise, 1 cinnamon stick, 4 cloves, 1 black cardamom pod, 1 tsp coriander seeds and 1 tsp fennel seeds in a dry frying pan over a medium heat, shaking the pan, until fragrant and a shade darker. Tie them in a square of muslin or put them in a large tea infuser.

Step 4: Return the bones to the clean pot with the 16 ¾ cups water, 1 ⅛ lb beef brisket and charred onion and ginger. Bring to the boil, then turn the heat down until only a few lazy bubbles break the surface. Skim off foam and fat with a ladle for the first 20 minutes.

Step 5: Keep the broth at that gentle simmer, uncovered, until the brisket is tender when pierced with a skewer. A rolling boil at this stage would make the broth cloudy and greasy.

Step 6: Lift out the brisket and drop it into a bowl of cold water for 10 minutes; this stops it darkening and drying. Drain, wrap and chill it so it slices neatly later.

Step 7: Keep simmering the bones for another hour. Add the spice bag for the last 40 minutes only; left in longer, the spices turn the broth bitter and medicinal.

Step 8: Strain the broth through a fine sieve lined with kitchen paper into a clean pan. You should have about 2.5 litres; top up with hot water if it has reduced further. Stir in the 4 tbsp fish sauce, ⅔ oz rock sugar and 2 tsp salt, then taste: it should be savoury, gently sweet and a little saltier than you would drink on its own, as the noodles absorb seasoning.

Step 9: To make ahead, cool the broth quickly by standing the pan in a sink of cold water, then refrigerate within 2 hours. It keeps for 3 days. Lift off the solid fat before reheating.

Step 10: Freeze the 9 oz beef sirloin or eye of round for 30 minutes until firm, then slice it across the grain as thinly as you possibly can, 1–2 mm. Lay the slices on a plate, cover and keep in the fridge until the last moment. The slices must be very thin, because the broth is their only cooking.

Step 11: Soak the 14 oz dried flat rice noodles (bánh phở) in warm water for 30 minutes while the beef firms up. Slice the cold brisket thinly across the grain.

Step 12: Bring a large pan of water to the boil. Cook the soaked noodles in batches for 30–60 seconds, until soft but still springy, then drain and divide among four deep, warmed bowls.

Step 13: Bring the broth to a full rolling boil over a high heat and keep it there while you assemble. Top the noodles with brisket slices, then lay the raw sirloin slices flat on top in a single layer. Scatter over the ½ white onion, 4 spring onions and ½ oz fresh coriander.

Step 14: Ladle the boiling broth straight over the raw beef, about 400 ml per bowl. The slices should turn from red to pale brown within seconds; push any pink pieces under the broth. For pregnant women, young children, older people or anyone with a weakened immune system, leave out the raw sirloin and use extra well-done brisket instead, or dip the raw slices in a ladle of the boiling broth for a minute until no pink remains.

Step 15: Serve at once with 2 limes, 2 red bird's eye chillies, 1 handful Thai basil and 5 ½ oz bean sprouts on a side plate. Hanoi diners keep sauces off the broth, but 4 tbsp hoisin sauce and 4 tbsp sriracha-style chilli sauce in a small dish for dipping the beef are welcome.