Begin by bringing a large pot of salted water to a boil. Add the fettuccine pasta and cook according to package instructions until al dente. Once cooked, reserve about 1 cup of pasta water, then drain the pasta and set it aside.
While the pasta cooks, make the creamy sauce. In a blender or food processor, combine the ripe avocados, garlic, lemon juice, milk, and a pinch of salt and pepper. Blend until smooth and creamy. If the mixture is too thick, add a bit of the reserved pasta water to reach your desired consistency.
Once the avocado mixture is smooth, add the finely shredded gouda cheese and fresh basil to the blender. Pulse a few times until the cheese is well incorporated into the sauce. Taste and adjust seasoning as needed.
In a large skillet over medium heat, add the drained fettuccine pasta. Pour the creamy avocado and gouda sauce over the pasta, tossing to coat the noodles evenly. If the sauce seems too thick, gradually add more reserved pasta water until you achieve a creamy and luscious coating.
Serve the pasta warm, garnished with toasted pine nuts and additional fresh basil. For those who like a bit of heat, sprinkle crushed red pepper flakes on top for an extra kick.
