Make the sauce: Heat Avocado oil in a heavy gauge pot. Saute the shallots, ginger, lemongrass, and cardamom. Add in the beets and stir. Allow the flavors to blend over medium heat for a couple minutes. Then add the sugar and stir until it is melted in. Add the rest of the ingredients (except salt and pepper) and bring to a boil. Taper temperature back to a simmer and allow the beets to cook at least 20 minutes. They should be soft and falling apart. Add more liquid and continue cooking if they aren't soft enough.
When the liquid is cooked down to barely covering the beets. And, the beets are soft enough to puree, remove the cardamom and lemongrass. Puree the Beets until a silky smooth sauce is created. Add a little orange juice if it is too thick. Season and set aside the sauce.
make the Cauliflower puree. Boil the potatoes in salted water. At the same time, toss the cauliflower in a little oil, salt, and white pepper. Roast at 350 degrees until it becomes soft (about 10 to 15 minutes). Try not to get too much color. But, make sure it is relatively dry. Strain the potatoes well. Puree the cauliflower in a food processor until smooth. Push the potatoes through a strainer or food mill and add to the food processor. add in butter, salt, and pepper. Puree everything together until smooth. Don't let the potatoes spend too much time in the processor or they will become gummy. Set aside and keep warm for service.
Prepare the fish: Fold the chopped nuts and herbs together. This can be done in a food processor or by hand. Be careful using a food processor, as the mixture can become too moist and clumpy. You want it to be dry enough to stick to your fish. Using the back of a teaspoon spread a very thin skim coat of dijon mustard on the fish. It should be just enough to hold the coating, not to make its own crust. Dip the fish fillets into the nut mix just to coat the top side evenly.
Heat the oil in a large saute pan over medium high heat. When it is just below the smoking point, add in the fish. Cook about 3 to 5 minutes per side. You want the Nut crust to be slightly browned. But, allow the green colors to shine through. It may take more time to cook the fish depending on the thickness of the fillets. If you want, you can sear the fish ahead of time. Leave it raw in the middle, and, finish it in a 350 degree oven. You want an internal temperature of 155 degrees. Again, cooking time depends on the thickness of the fish.
Cook the vegetables. Heat oil in a saute pan over high heat. Add in the green vegetable of your choice. Season with salt and pepper, toss until just cooked through (about 30 seconds to 1 minute).
Plate the dish: Make a bed of the cauliflower puree in the middle of the plate. Top with the fish. Either drizzle the sauce over the top or pool it around the puree. Or you can do a little of both. Garnish the plate with the vegetables, some microgreens, and citrus is desired.