For the most flavor, supplement standard cremini mushrooms with other varieties such as shiitake, chanterelle, maitake, morel, or oyster. But even if you just use creminis, this will still be delicious!

Prepare, using 2 rimmed baking sheets:

To ensure the mushrooms roast evenly, switch the baking sheets and rotate them halfway through cooking. As the mushrooms roast, heat in a medium saucepan until steaming:

Cover and remove from the heat. Melt in a large saucepan over medium heat:

Whisk in:

Let the flour sizzle in the butter until golden, about 5 minutes. Gradually whisk in the porcini-infused milk (leave the dried porcinis in the milk). Bring to a simmer, whisking frequently, and cook until thickened, about 5 minutes. Remove from the heat. When the mushrooms have finished roasting and cooled slightly, coarsely chop them and stir into the milk mixture, along with:

Season to taste with:

Preheat the oven to 375°F. Grease a deep 13 × 9-inch baking dish, 13 × 9 × 2-inch baking pan, or lasagne pan. Prepare:

Have ready:

For dried noodles, cook in a large pot of boiling salted water until barely tender. Drain the pasta, rinse under cool water, and blot it dry. For fresh lasagna noodles, do not boil. Spread a thin layer of mushroom sauce on the bottom of the prepared pan. Cover with a layer of noodles, overlapping them slightly. Top with one-third of the ricotta mixture and one-quarter of the mushroom sauce. Repeat three more times, topping the last layer of pasta with the remaining mushroom sauce. Sprinkle on top:

Cover the lasagne with foil and bake 30 minutes. Remove the foil and bake until well browned and bubbling, about 15 minutes more. Let stand for 15 minutes before serving.