Heat oven to 400°F Grease a 9" square baking dish with 1 tbsp oil.
Bring large pot of water to boil and salt it. Boil the cauliflower until very tender, about 20 - 25 minutes. Scoop the cauliflower out and place in blender or food processor. Reserve the boiling water and bring it back to a boil. Add the pasta and cook about 5 minutes and drain. It should still be somewhat chalky and not completely done.
While the cauliflower is boiling, put the stock with the bay leaves in a small saucepan over medium low heat. Just when bubbles start to form, turn off the heat and let stand. When ready to process the cauliflower, remove the bay leaves from the stock and add two cups stock to the processor with the cauliflower. Add 2 tbsp olive oil, the cheese, mustard, nutmeg and a sprinkling of salt and pepper. Process until creamy. You may have to work in two batches. If the sauce seems too thick, add the remaining stock. Taste and adjust seasoning.
Pour the sauce over the pasta, toss, and spread the mixture evenly in the baking dish. (At this point you could cover and refrigerate up to a day, but be sure to return to room temperature before baking.).
Sprinkle the top of the dish with the Parmesan and bread crumbs. Bake until the pasta is bubbling and the crumbs turn brown, about 15 - 20 minutes. Serve hot.