Once you get the hang of this recipe, you can modify it any way you like. For speed, you skip the mushrooms and/or use readymade marinara sauce rather than sauteeing your own onion, carrot, celery, and garlic (you can even skip the proscuitto, red pepper flakes, and rosemary). Whatever you do, it's still awesome. (But DO try the whole shebang when you have time; it's next level.) You can make, cover, and refrigerate the Bolognese up to 2 days in advance or assemble, cover, and refrigerate the whole lasagna a day in advance, then let it sit at room temperature for 1 hour prior to baking.
In a small bowl, combine the porcini mushrooms with the boiling water and let sit for 20 minutes. Using a slotted spoon, remove the porcini and squeeze the excess liquid back into the bowl.
Raise the heat to medium and stir in the minced prosciutto, red pepper flakes, and rosemary. Stir in the ground beef, then spread the mixture in a single layer, letting the meat cook undisturbed for 5 minutes. Stir, breaking up the meat with the spoon, then lower the heat to medium-low and cook for 7 minutes more, stirring occasionally and breaking up the meat.
Bring a large pot of well-salted water to a boil. Add the greens, cook for 2 minutes, then transfer to a strainer to cool, reserving the cooking water. When cool enough to handle, squeeze out the excess water, coarsely chop the greens, and stir them into the ragù.
Return the reserved cooking water to a boil, add half of the noodles, and cook, stirring occasionally, for 4 minutes. Transfer to a colander to drain. Repeat with the remaining noodles. Drain, arrange in one layer on a baking sheet, and cover with a damp towel until needed.
Preheat the oven to 375oF. Remove and discard the cheese rind from the ragù. Spread 1⁄2 cup of the ragù in a 9 by 13-inch baking dish. Top with a layer of noodles. Spread 2⁄3 cup béchamel over the noodles, then top with 1 1⁄4 cups of the ragù and 1⁄2 cup Parmigiano-Reggiano. Repeat to create two additional layers of noodles, béchamel, ragù, and cheese. Top with a layer of noodles. Spread the remaining béchamel over the last noodle layer, sprinkle with the remaining 1⁄4 cup Parmigiano- Reggiano. Dot with the butter and sprinkle with the prosciutto strips and rosemary.