In a large pot, fill with water and add a generous amount of salt. Bring to a rolling boil and cook spaghetti according to package instructions until al dente.

Heat olive oil in a large skillet over medium heat. Add chopped onion and jalapeño, sauté for 3-4 minutes until onion is translucent.

Add minced garlic and fresh spinach to the skillet, cooking for an additional 2-3 minutes until spinach wilts.

Transfer mixture to a blender with roasted poblano peppers, cilantro, sour cream, bouillon, and milk. Blend until smooth.

Return sauce to the skillet over low heat. Stir in cream cheese until melted and incorporated; season with salt and pepper.

Add drained spaghetti to the sauce, tossing to coat. If too thick, add reserved pasta water gradually until desired creaminess is achieved.

Serve hot, garnished with optional toppings.