How to Make It
In a large saucepan, heat 1 tablespoon of the vegetable oil. Add the bacon and cook over moderate heat until crisp, about 7 minutes. Using a slotted spoon, transfer the bacon to a plate.
Pour off all but 1 tablespoon of the fat in the saucepan. Add the remaining 1 tablespoon of oil and when it's hot, add the onions, poblanos and garlic and cook over moderately high heat until softened, about 5 minutes. Add the shiitake, cover and cook, stirring occasionally, until softened, about 5 minutes. Uncover and stir in the flour. Gradually add the stock and bring to a boil, stirring. Cook the soup over moderately high heat until thickened. Add the oregano and simmer over low heat for 5 minutes. Season the soup with salt and pepper and stir in the bacon.
Ladle the soup into bowls and serve with the tomato, avocado, red onion, cilantro and lime wedges.