01 -
Heat 2 tablespoons olive oil and 2 tablespoons butter in a large sauté pan over medium heat. Add sliced leeks and season with ½ teaspoon salt and ½ teaspoon sugar. Cook, stirring occasionally, until golden and caramelized, about 20 minutes. If the pan gets too dry, add 1-2 tablespoons of water.
02 -
Add the sherry to the pan and continue to cook until the wine has reduced. Remove the leeks from the pan and set them aside.
03 -
In the same pan, melt the remaining tablespoon of butter. Spread mushrooms in an even layer, allowing space between them. Let sit until browned, about 4 minutes, then flip and brown the other side. Season with salt and pepper.
04 -
Add minced garlic and sage to the mushrooms, sautéing for 1 minute. Return the leeks to the pan and add ¾ cup heavy cream, balsamic vinegar, and lemon zest. Bring to a simmer and cook until thickened, about 2-3 minutes. Season with additional salt and pepper as needed.
05 -
Meanwhile, cook the fettuccine until al dente, reserving 1 cup of the pasta cooking water.
06 -
Add the cooked fettuccine, 1 cup reserved pasta water, Gruyere cheese, and black pepper to the sauce. Toss to coat and simmer for 2 minutes or until the cheese is melted and the pasta is well coated. Adjust seasoning with salt and pepper as needed.
07 -
Portion pasta into 4 bowls, garnishing with toasted pine nuts. Serve immediately.