Preheat oven to 400 degrees F
Begin by buttering four 2-cup soufflé dishes (or one 8-cup soufflé dish) and dust with grated parmesan to keep the soufflé from sticking.
In a sauté pan over medium-high heat, add the oil. Add the dandelion greens and sauté until wilted, a couple of minutes. Add the garlic, lemon juice, salt and pepper and stir for a minute more. Add the water and simmer until the water has evaporated. Greens should be nice and soft. Turn off the heat and set the greens aside.
In a saucepan over medium heat, melt the butter. Add the flour and whisk stirring constantly until foamy, being careful not to brown. Take the pan off the heat and add the warm milk, whisking vigorously until the mixture becomes smooth. Whisk the cayenne pepper. Add the egg yolks and whisk well. Stir in the reserved dandelion greens. Season to taste with salt and pepper.
In the bowl of an electric mixer, using the whisk attachment, whip the egg whites with a pinch of salt until stiff.
Stir one quarter of the beaten egg whites into the butter and flour mixture to lighten. Stir in the Gruyere cheese. Gently fold the remaining egg whites into the mixture until just incorporated.
Place the soufflé dishes on a baking sheet, and gently divide the batter into the prepared dishes. Sprinkle parmesan cheese on top. Reduce the heat to 375 degrees and bake the soufflés for about 15 minutes (a bit longer if making one large soufflé) They're ready when they are puffed up (and perhaps cracked), and golden brown on top. Avoid opening the oven if possible during baking!