1️⃣ Caramelize the Leeks:

Heat 2 tbsp olive oil and 2 tbsp butter in a large sauté pan over medium heat.

Add the sliced leeks, ½ tsp salt, and ½ tsp sugar.

Cook for about 20 minutes, stirring occasionally, until golden and caramelized.

If the pan gets too dry, add 1-2 tbsp water to prevent burning.

2️⃣ Deglaze with Sherry:

Pour in the sherry wine and cook until it has reduced.

Remove the leeks from the pan and set them aside.

3️⃣ Cook the Mushrooms:

In the same pan, melt 1 tbsp butter.

Spread the mushrooms in an even layer, leaving space between them.

Let them cook undisturbed for 4 minutes until browned.

Flip and cook the other side. Season with salt and pepper.

4️⃣ Build the Sauce:

Add the minced garlic and sage leaves, sauté for 1 minute.

Return the caramelized leeks to the pan.

Stir in ¾ cup heavy cream, balsamic vinegar, and lemon zest.

Bring to a simmer and cook until thickened (about 2-3 minutes).

Adjust seasoning with salt and pepper.

5️⃣ Cook the Pasta:

While making the sauce, cook the fettuccine in salted boiling water until al dente.

Reserve 1 cup of pasta water before draining.

6️⃣ Combine Pasta and Sauce:

Add the fettuccine to the sauce along with 1 cup of reserved pasta water, Gruyere cheese, and black pepper.

Toss well and simmer for 2 minutes, until the cheese melts and coats the pasta.

Taste and adjust seasoning if needed.

7️⃣ Garnish and Serve:

Portion the pasta into 4 bowls.

Sprinkle with toasted pine nuts for extra crunch.

Serve immediately and enjoy!