1. Cook the spaghetti noodles in salted water according to package instructions until al dente. Drain and set aside.
2. Roast the poblano peppers until the skin is charred. Place them in a sealed container or plastic bag to steam for 10 minutes.
3. Peel the skin off the peppers, remove the stems and seeds.
4. In a blender, add the roasted poblanos, cream cheese, sour cream, milk, garlic, onion, chicken bouillon, cilantro, and salt. Blend until smooth.
5. In a large skillet, melt the butter over medium heat.
6. Pour in the poblano sauce and stir occasionally until the sauce starts to bubble and thicken.
7. Add the cooked spaghetti noodles and mix well to coat evenly with the sauce.
8. (Optional) Transfer pasta to a broiler-safe baking dish, sprinkle shredded cheese over the top, and broil for 3–5 minutes until melted and bubbly.
9. Garnish with fresh cilantro and serve warm.