Heat Oil: In a large skillet, heat 1 tablespoon of olive oil over medium-low heat.
Cook Onions: Add the sliced onions and cook, stirring occasionally, for 20-25 minutes or until golden and caramelized. Reduce the heat if they start browning too quickly. Remove from the skillet and set aside.
Cook the Pasta
Boil Water: Bring a large pot of salted water to a boil. Add the farfalle and cook according to package instructions until al dente. Reserve 1/2 cup of pasta water before draining.
Sauté the Mushrooms and Spinach
Heat Oil: In the same skillet, add the remaining tablespoon of olive oil and heat over medium heat.
Sauté Garlic and Mushrooms: Add the minced garlic and cook for 1 minute until fragrant. Add the mushrooms and sauté for 5-6 minutes or until browned.
Add Spinach: Stir in the fresh spinach and cook for 2-3 minutes until wilted.
Combine and Serve
Mix Ingredients: Add the caramelized onions back to the skillet along with the cooked pasta. Toss to combine, adding a bit of reserved pasta water if needed for a cohesive sauce.
Season and Serve: Season with salt, black pepper, and thyme. Serve with a sprinkle of Parmesan and garnish with fresh parsley if desired.