Heat the oven to 400°F. Grease a 9-inch square baking dish or equivalent casserole with a little oil.

Add the stock, milk, peppercorns and the bay leaves in a small saucepan and heat over medium-low heat. When small bubbles appear along the sides, about 5 minutes later, turn off the heat and let stand and steep.

Bring a large pot of water to a boil and salt it. Cook the cauliflower in the boiling water until very tender, 20 to 25 minutes. Scoop the cauliflower out of the water with a slotted spoon and transfer it to a blender or food processor.

Add the pasta to the still boiling water and cook until still somewhat chalky inside and not yet edible, about 5 minutes. Drain and return to pot.

Remove the peppercorns and bay leaves from the stock or stock/milk mixture. Carefully process the cauliflower with 2 cups of the stock/milk mixture, the 2 tablespoons oil, the cheese, mustard, nutmeg, and a sprinkling of salt and pepper. (It’s very likely this will need to be done in batches; don’t fill the blender more than 3/4’s full and be careful when processing hot foods in a blender. Don’t cover until ready to blend, loosen the lid or vent slightly and firmly hold the lid in place using a towel to protect hands.)

The mixture should be just slightly soupy; if the sauce seems too thick, add the remaining 1⁄2 cup stock or stock/milk mixture. For a small head of cauliflower, the 2 cups of liquid will most likely be sufficient, with a larger head, the whole 2 1/2 cups should be sufficient. Taste and adjust the seasoning.

Pour the sauce over the pasta, toss to mix. Add to the greased baking dish or casserole and spread the mixture evenly in the dish. The dish may be made to this point, covered, and refrigerated for up to a day; return to room temperature before proceeding.)

For the topping, mix together the Parmesan and bread crumbs with the butter or oil. Sprinkle over the top of the casserole. Bake until the pasta is bubbling and the crumbs turn golden brown, 15 to 20 minutes. If the casserole is hot and bubbly but the breadcrumbs haven’t yet nicely browned, turn the broiler on for a few minutes and watch carefully. Serve hot.

Note on bread crumbs: Starting with toasted breadcrumbs will make a more appealing topping. 15 to 20 minutes is not enough time to brown plain white bread crumbs.