Put the haddock fillets in the steamer. Cover tightly and steam for 6-7 minutes, depending on the thickness of the fillets: they should have turned opaque and be flaking slightly but is still moist.
Remove onto warm plates and keep warm.
Place the pak choi in the steamer and steam for a minute or two. Meanwhile make the dressing by whisking everything together in a small bowl.
Arrange the steamed haddock and pak choi on warmed plates and drizzle over the dressing to serve.
Steamed pak choi or vegetables of your choice.