Saute onions and chopped garlic in a little olive oil. Add chopped cauliflower and cover the pot, reduce heat slightly. Cook stirring every few minutes until the cauliflower starts to brown slightly.

Add the white wine and cook uncovered for 5 minutes. Add enough shellfish stock to cover the cauliflower by about 1/2 inch. Bring to a simmer.

Thicken slightly. I prefer to thicken soups with a flour/water slurry, as opposed to a roux, it introduces less fat and it is easier to control. To prepare your slurry, mix flour with water in a small bowl to a consistency of a very, very thin paste. Pour in a little at a time, through a strainer, into the soup, stirring as you go. When the liquid is thickened to the consistency of a very light sauce, that's fine. Remember that the cauliflower will thicken the soup somewhat as it breaks down.

Once the slurry has been added simmer the soup for 1/2 hour. (Note: The soup needs to cook for at least 1/2 hour once flour has been introduced to fully cook out the raw flour.) When the cauliflower becomes very soft, break it up with a whisk or potato masher and continue simmering.

Add chopped fresh tarragon to taste and heavy cream, or half and half, again to taste.

You can hold the soup at this point. When ready to serve have shredded fresh spinach and thinly sliced scallops at hand. Bring soup back to simmer, add the scallops, cook for 30 seconds more. Then add the spinach and cook for 10 seconds and serve. Top with crostini garnish, if desired.