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