Roast poblanos under broiler until charred (5-7 minutes per side). Steam in plastic bag, peel, and remove seeds.
Cook spaghetti in salted water until al dente. Reserve 1 cup pasta water before draining.
Blend poblanos, spinach, cilantro, crema, onion, garlic, and bouillon until smooth.
Heat sauce in large pan, add cooked pasta, toss until well coated.
Add pasta water if needed for desired consistency.
Top with cheese and cilantro. Serve hot.