Step 1Heat the oven to 300 degrees. Spread the walnuts on a baking sheet and toast them until fragrant, 10 minutes. Turn them out onto a clean dish towel and rub them with the towel to remove as much of the skins as possible. Set aside.
Step 2Roast the chile over a flame or under the broiler until it is evenly charred all over, 5 minutes. Wrap the chile in plastic wrap and let it cool, then unwrap and slip off the skin. Remove seeds, stems and all blackened bits. Cut it in half lengthwise. Coarsely chop one half, finely dice the other and set aside.
Step 3In a heavy medium saucepan, melt the butter over medium heat. Add the garlic and sprinkle with the salt. Saut? for 2 or 3 minutes, then add the walnuts, the coarsely chopped poblano, the chicken stock and the cinnamon stick. Simmer for 30 minutes.
Step 4Remove the cinnamon stick. Let the soup cool slightly, then transfer to a blender and pur?e on highest speed until smooth. Wipe the pot clean and return the soup to it. Bring to a simmer. Taste and adjust the seasoning, then swirl in the crema.
Step 5Pour the soup into espresso cups and top each first with a few sprinkles of the diced poblano and the pomegranate seeds (reserve leftover pomegranate seeds for another use).