Preheat the oven to 450 degrees F. In a small saucepan, reduce the heavy cream by half over low heat. Remove from the heat and set aside.
In a medium saute pan, cook the cauliflower, garlic and onion in 3 tablespoons oil over medium heat, stirring occasionally, until golden brown. If the cauliflower starts to brown, deglaze the pan with a splash of white wine or water. Remove from the heat and let cool, 5 minutes.
Blend together the cream, cauliflower mixture, mascarpone, sherry vinegar and salt and white pepper to taste in a blender.
Heat a cast-iron skillet with the remaining 3 tablespoons oil over high heat until very hot. Sear the sea bass, skin-side down, for 3 minutes. Transfer to the oven and bake until opaque, 5 to 7 minutes.
Meanwhile, fill a large Dutch oven about halfway with oil and bring to 375 degrees F. Fry the leek tops until dark and crispy.
Divide the cauliflower puree among 4 plates, then top each with a piece of sea bass. Garnish with the fried leek tops, lemon peel, radish slices, chives and parsley and serve immediately.
This recipe was created by a contestant during a cooking competition. It has not been tested for home use.