Heat your oven to 180°C/Fan 160°C/Gas 4. Line a baking tray with foil and brush it with 2 tsp oil. Place the cod fillets on the tray, skin side down.
Press ½ tbsp sesame seeds onto each fillet, covering the top as much as you can. Bake for 10-15 mins till the cod is opaque and flakes easily when pressed with a fork.
While the cod cooks, separate the pak choi leaves and slice the stalks. Shred the larger leaves. Trim the broccoli and break into florets.
Warm 2 tsp oil in a wok or deep frying pan. Add the broccoli and pak choi stalks. Stir fry for 5-6 mins till the veg start to soften and char a little.
Add the hoisin sauce to the pan with 1 tbsp of the tamari and a pinch of dried chilli flakes. Pour in 100 ml boiling water.
Stir fry for another 3-4 mins till the veg are tender. Add the pak choi leaves and stir fry for another 1-2 mins till they’re just wilted.
Taste the stir fried veg and add a little more tamari if you think it needs it. Serve the cod with the stir fried greens and some more chilli flakes, if you like.