On a dry skillet or over a flame, char the daikon radish, onions, cabbage wedges, and halved ginger until charred. Set aside.
In the same skillet, cook mushrooms and oil until browned.
Transfer the charred ingredients and mushrooms to an Instant pot and fill with 2 L water. Press everything down to be submerged under the water, be sure to be under the max fill line or the pot won't come up to pressure.
Pressure cook on soup for 15 minutes, turning the vent to "Sealing". Once cooked, either let it release pressure naturally or manually (be careful as there will be a lot of steam with this amount of liquid).
Remove the cabbage, onion, ginger, and daikon pieces but you can leave the mushrooms if you'd like to eat them. Using a nut bag or a fine mesh sieve, steep the star anise, coriander seed, cardamom, cassia bark (or cinnamon), and cloves for 10 minutes to infuse.
Season with 3.5 tbsp mushroom broth powder, then serve with your favourite pho accoutrements!