Prepare the Pasta

1. Boil the Pasta: Start by bringing a large pot of salted water to a boil. Add the bow tie pasta and cook according to the package instructions, usually about 9-11 minutes. Stir occasionally to prevent sticking.
2. Drain the Pasta: Once the pasta is al dente, drain it, reserving about 1 cup of pasta water. Set the pasta aside.

Caramelize the Onions

3. Cook the Onions: While the pasta is cooking, heat 1 tablespoon of olive oil in a large skillet over medium heat. Add the thinly sliced onions and a pinch of salt. Cook the onions, stirring occasionally, for about 10-15 minutes, until they become soft, golden brown, and caramelized. If the onions start to brown too quickly, reduce the heat to low and continue to cook until they’re deeply caramelized.
4. Set the Onions Aside: Once the onions are caramelized, remove them from the skillet and set them aside in a bowl. This will allow them to retain their sweetness.

Cook the Mushrooms and Garlic

5. Sauté the Mushrooms: In the same skillet, add another tablespoon of olive oil and increase the heat to medium-high. Add the sliced mushrooms and sauté for 5-7 minutes, until they release their moisture and become golden brown. Stir occasionally to ensure even cooking.
6. Add the Garlic: Add the minced garlic to the mushrooms and cook for another 1-2 minutes, until fragrant.

Create the Creamy Sauce

7. Add the Cream and Milk: Lower the heat to medium and pour in the heavy cream and milk. Stir well to combine, creating a smooth, creamy sauce. Let it simmer for 2-3 minutes to thicken slightly.
8. Add Parmesan: Stir in the grated Parmesan cheese, allowing it to melt into the sauce. Season with salt, pepper, thyme, and red pepper flakes (if using). Taste and adjust the seasoning as needed.

Combine Pasta, Vegetables, and Sauce

9. Add the Spinach: Stir in the fresh spinach and cook for 2-3 minutes, just until it wilts and softens. The spinach will blend seamlessly into the creamy sauce.
10. Combine the Pasta and Sauce: Add the cooked bow tie pasta to the skillet with the creamy mushroom sauce. Toss everything together, adding a bit of reserved pasta water if needed to loosen the sauce.

Finish and Serve

11. Reintroduce the Caramelized Onions: Once the pasta is well coated with the sauce, stir in the caramelized onions and heat everything through for another 1-2 minutes.
12. Serve: Divide the creamy bow tie pasta into serving bowls. Garnish with freshly chopped parsley or basil and an extra sprinkle of Parmesan, if desired.