Arrange a rack at the center position, and heat the oven to 350 degrees. Grease four 6-ounce ramekins or souffles. Cover the bottom of each with a parchment circle cut to fit, and grease the parchment. Place the ramekins in a baking pan large enough to hold them comfortably.
Fill a medium-size saucepan 2/3 full with lightly salted water and bring to a boil over high heat. Add the cauliflower florets and cook until very tender when pierced with a knife, for about 10 minutes. Drain the florets well in a colander and pat dry with a clean kitchen towel. Puree the cooked florets in a food processor until almost smooth.
In a medium-size bowl, whisk together the eggs, cream, milk, 1/2 cup parmesan cheese, 1/2 teaspoon salt, nutmeg and cayenne pepper. Add the cauliflower puree and whisk well. Divide the mixture evenly among the ramekins. Pour enough boiling water into the baking pan to come halfway up the sides of the ramekins.
Carefully place the pan in the oven. Bake until the flans are set and a small sharp knife or tester inserted into the centers comes out clean, for about 35 minutes. Using potholders, remove the ramekins from the pan to a cooling rack for 5 minutes.
(The flans can be prepared 1 day ahead. Cool, cover with plastic wrap, and refrigerate. Bring to room temperature and reheat, uncovered, for about 15 minutes on a baking sheet in an oven that has been heated to 350 degrees.).
Run a sharp knife around the inside edges of the ramekins. Unmold onto a flat work surface and peel off the parchment paper. Sprinkle each flan with parmesan cheese and parsley.