Trust me this is one of the easiest fanciest meals you can prepare, and you will keep returning to it every so often. The sauce will keep for quite a while in the fridge so make more. Don't be disheartened by the Asian ingredients. They are long-shelf items that you buy once and keep forever, so just get them next time you pass by an Asian market. The puree will also be edible within the week so store leftover (in the occasion there is any!).
For the teriyaki sauce (adopted from Morimoto's "Japanese Homecooking" book), place in a pot and bring to a boil:
Sake, 1/2 cup
Mirin, 1/2 cup
Soy, 1/2 cup
Sugar, 1/2 cup
Onion, 1 pc, skin on, cut in quarters
Ginger, 10 thin slices, unpeeled
Garlic, 2 cloves, skin on, and crushed
then turn heat down and simmer for 15 minutes. Discard solids and keep sauce in a jar. You can reduce it to the consistency of a glaze at any time (in this recipe I reduce it to a thin glaze, simmering it down until it coats the back of a spoon, but still drips as a thin ribbon).
For the cauliflower puree (from Thomas Keller's "The French Laundry Cookbook", in which it evolves into a Panna Cotta), in a small pot place:
Cauliflower florets from half a piece, about 250 gr
Butter, 30 gr
Water, about 500ml (1 and 1/2 cup), you do not want too much water. You want it just below the surface of the florets.
When the water starts to boil, turn heat down and simmer for about 20 minutes. The cauliflower should have broken down to small pieces, and the water should be almost gone. Add:
Heavy cream, 200 ml (1 cup roughly, slightly less)
Simmer for 10 minutes and puree using a hand blender. Adjust seasoning (salt). Store in an airtight container in the fridge. Before use, reheat gently, either in the oven covered with foil, or very carefully in a pot over low heat with barely any boiling water, and stirring when needed. The texture of this puree is soooo silky you do not want to ruin it by drying it out.
Bake the salmon in the oven at 200 degrees Celsius for 15 minutes. Serve with the cauliflower puree, and pour the sauce on top. Garnish with either, or all of:
Spring Onion tops