Preheat a water bath to 85C / 185F.
Wash the cauliflower well and trim off all the leaves. Save the leaves and bag them separately with 1 tablespoon of butter and salt to cook for 1 hour, then reserve for plating.
Cut the stem off even with the bottom of the cauliflower. Using your knife, insert it deep into the stem/core of the cauliflower to make an X.
Bag the cauliflower with the butter, vacuum seal, and cook at 185°F until tender (2 - 3 hours) (if cooking at 194°F, check around 1.5 - 2 hours). Set aside on counter to cool for 15 - 20 minutes while oven preheats.
Mix all ingredients except oil in a small bowl. If you have a chamber sealer, you can pull a vacuum or two to allow vinaigrette to infuse fully into shallots and garlic.
Slowly drizzle oil in until you have a smooth emulsification. Season with salt and pepper to taste.
Preheat Oven to 375°F.
Remove cauliflower from the bag. Save the purge and use it as you would any vegetable broth.
Lightly coat the cauliflower with olive oil, and roast until light golden brown, 15 - 20 minutes.
Remove from the oven. Lightly pull apart the cauliflower florets so it still holds its shape but there are gaps throughout. Sprinkle liberally with panko and parmesan, then return to the oven for 5 - 7 minutes until the panko is crispy.
To plate, place the cauliflower on a serving dish, and place the cooked leaves around it as they were on the original raw head. Drizzle liberally with vinaigrette and serve.
