Bring a large pot of salted water to a boil and cook the pasta until just al dente, following package instructions. Drain and set aside, reserving a cup of pasta water.
While the pasta cooks, slice the cleaned leeks thinly, discarding the tough green tops, and set aside. Clean the mushrooms with a damp cloth and slice them evenly.
Heat the olive oil in a large skillet over medium heat until shimmering. Add the sliced leeks and cook, stirring frequently, until they soften and turn golden, about 10-12 minutes. They should smell sweet and caramelized.
Push the leeks to one side of the skillet. Add the sliced mushrooms to the other side and cook, stirring occasionally, until browned and earthy, about 8 minutes. Mix the mushrooms and leeks together once browned.
Add the minced garlic to the skillet and cook until fragrant, about 30 seconds, stirring constantly to prevent burning.
Pour in a splash of the reserved pasta water and stir to create a light, flavorful sauce that coats the vegetables.
Toss in the drained pasta and stir thoroughly to coat it with the leek and mushroom mixture. If needed, add more pasta water to loosen the sauce until it’s glossy and clingy.
Remove the skillet from heat. Squeeze fresh lemon juice over the pasta for a bright finish, and season generously with salt and freshly ground black pepper to taste.
Serve immediately, garnished with extra herbs or cheese if desired, and enjoy the warm, tender textures and earthy aroma of this simple yet satisfying dish.
