Bring a large pot of water to boil. Add 2 tablespoons of salt and the juice of 1 lemon. Add cauliflower florets and cook, uncovered, for 15 minutes. Drain the cauliflower.
While the cauliflower cooks, heat a large pot or dutch oven over medium heat. Add the leeks and stir to coat, season with salt and cook until very tender, 15 minutes. Adjust the heat as needed to prevent browning. Add the cauliflower and stock and bring to a simmer. With a slotted spoon, carefully transfer the leeks and cauliflower to a blender with some of the stock (note: work in batches to prevent over-filling the blender). Puree until smooth.
Toast the Pine Nuts - Infuse the Oil
In a small pan, warm the olive oil with the pine nuts over low to medium heat. Stir and cook just until the nuts begin to turn golden. Drain the oil immediately into a small bowl, reserving the pine nuts for garnish.
Finish the Potage
Season the potage with salt and pepper to taste and whisk in the pine nut oil. Serve the soup garnished with a few bits of lime, pine nuts, and a sprinkle of parsley. Cayenne is also a lovely flourish if you like a little heat.