Combine 7 cups of water and the salt in a medium pot and bring the water to a boil over high heat. Gradually add the polenta, whisking as you pour. Keep whisking until the polenta starts to thicken and looks like it's one with the water, about 2 minutes. Turn the heat to low (the polenta should steam and tremble, but only rarely erupt with bubbles) and cook, stirring every now and again, until the polenta is tender but still coarse in texture, about 45 minutes.
Stir in the olive oil, kale puree, and most of the Parmesan and keep cooking, stirring occasionally, for a few minutes more. Take the pot off the heat and fold in 2 tablespoons of the mascarpone (it's nice to run into a little pocket of mascarpone, so don't stir too much). Top with the remaining mascarpone and Parmesan, and as much black pepper as you'd like.
Put 4 of the garlic cloves in a medium pot, fill it with water, cover, and bring the water to a boil over high heat. Add enough kosher salt so that the water tastes slightly salty and add the kale, prodding to submerge it. Cook uncovered until the kale is tender and tears easily, 2 to 3 minutes.
Fish out the boiled garlic cloves from the pot and reserve them. Drain the kale in a colander and when it's cool enough to handle, squeeze out as much water as you can. Roughly chop the kale, the boiled garlic, and the raw garlic.
Combine the kale, garlic, and Maldon salt in a food processor. Process, stopping occasionally to prod and stir, for about 45 seconds, then add the oil and process, stirring once or twice, to a fairly smooth puree. Whenever I make this at one of my restaurants, I use a Vita-prep to make the puree silky smooth, but I like a slightly coarse puree too.
The puree keeps in an airtight container in the fridge for up to 5 days.
Before I use Tuscan kale, I like to remove the thick stems. I've seen home cooks do this with a knife, which you can do if you fancy. I have a quicker way. Working one leaf at a time, firmly grab the end of the stem with one hand. With the other, use your thumb and index finger to firmly pinch together the bottom of the leaf on either side of the stem and pull away from the stem end, stripping off the leaves in one go.
From A Girl and Her Greens by April Bloomfield with JJ Goode. Copyright 2015 April Bloomfield. Excerpted by permission of Ecco, an imprint of HarperCollins Publishers.