In a medium bowl, soften butter and add macadamia nuts, garlic, thyme, parsley, lemon juice, zest, salt and pepper and mix well. Season fish with salt and pepper. Sear fish on both sides and cool. Spoon macadamia nut butter over the fish than bake in the oven for about 8 minutes at 350°.
In a sauce pan, add the sweet Thai chili sauce, coconut milk, ginger, garlic, cilantro and lime juice and heat until warm throughout. To plate, place the fish with poached choy sum and spoon sauce around the fish and enjoy.