Preheat the oven to 220C then place the quartered onions and sliced ginger on a baking tray and cook until lightly charred (approx 20-30 min).
Put the strained brisket stock in a saucepan and add the fennel & coriander seeds, cinnamon, cloves, star anise, cardamom, chilli flakes, peppercorns, sugar & a pinch of salt.
Add the charred onions and ginger to the saucepan, bring to the boil then turn the heat to low, cover and gently simmer for 30-40 minutes until the stock has a good, spicy flavour.
Strain the stock and discard the onions, ginger and spices. Return the stock to the rinsed saucepan. To increase the flavour, add a little ground allspice or Chinese 5 spice powder.
Stir in 1 tbsp of the fish sauce and 1 tbsp of the soy sauce. Keep the broth warm.
Divide the prepared carrot, courgette, onions & greens between two large bowls.
Reheat the brisket slices in a microwave (approx 1 min) and place on top of the vegetables in the bowls.
Pour the hot, spiced broth over the vegetables then dress with spring onions, herbs and sliced chillies.
Serve the pho, allowing each person to add lime juice, fish, soy and chilli sauces at the table according to their taste.