Begin by bringing a large pot of salted water to a boil over high heat. Once boiling, add the dry spaghetti and cook according to package instructions until al dente, typically about 8-10 minutes. Reserve 1 cup of pasta water, then drain the spaghetti in a colander. Set aside while you prepare the creamy sauce.

In a large skillet, heat 2 tablespoons of olive oil over medium heat. Add the chopped onion and diced jalapeño, sautéing for approximately 3 minutes until the onion becomes translucent.

Stir in the minced garlic and fresh spinach leaves, cooking for about 2 minutes until the spinach wilts down. Once wilted, transfer this aromatic mixture to a blender.

In the blender, combine the cooked spinach mixture with the roasted poblano peppers, fresh cilantro, sour cream, and bouillon. Pour in 2/3 cup of milk to achieve a smooth consistency. Blend until the sauce is silky and well-combined.

Return the blended green sauce to the skillet over low heat and add cubed cream cheese. Stir well, allowing the cream cheese to melt and integrate into the sauce, which should take around 4 minutes.

Introduce the reserved spaghetti to the skillet with the creamy sauce. Toss everything together, ensuring the pasta is well-coated. If the sauce seems too thick, gradually incorporate the reserved pasta water until you achieve your desired creaminess. Season to taste with salt and pepper.

Plate the vibrant Mexican Green Spaghetti and garnish with additional chopped cilantro, crumbled cotija cheese, or toasted pepitas for extra crunch.