Slice two medium onions thinly. In a large skillet, heat 2 tablespoons of olive oil over medium heat. Add the onions and a pinch of salt, stirring occasionally. Cook for 15-20 minutes until caramelized.

Add 8 ounces of chopped mushrooms and 2 cloves of minced garlic to the skillet. Sauté for about 5-7 minutes, until the mushrooms are tender and the mixture is fragrant.

In a large pot, bring water to a rolling boil. Add a generous amount of salt and cook 12 ounces of farfalle pasta according to package instructions until al dente, around 10-12 minutes. Reserve 1 cup of pasta water before draining.

Add the drained farfalle pasta to the skillet with caramelized onions and sautéed mushrooms. Toss gently over low heat. Fold in 4 cups of fresh spinach and let it wilt for 2-3 minutes.

Stir in 1/4 cup of reserved pasta water gradually to reach desired creaminess, tossing until the pasta is well coated.

Serve immediately, garnished with grated Parmesan cheese and toasted pine nuts if desired.