Preheat oven to 450°F. On foil lined baking tray, roast tomatoes, onions and garlic until nicely charred, about 10 minutes. Remove vegetables from tray, peel garlic and reserve.
Meanwhile, toast chiles on dry skillet for 2 minutes, or until fragrant. Boil water in a kettle, and soak toasted dried chiles, covered with the boiling water until rehydrated, about 10 minutes. Drain chiles and reserve.
In large frying pan, heat 2 Tbsp vegetable oil. Add mushrooms and 1//4 tsp kosher salt and cook on medium high heat until they are nicely caramelized, about 10 minutes. Add epazote and reserve.
In blender jar, blend the roasted tomatoes, onions, garlic, rehydrated chiles and half of the mushrooms. Process until smooth.
In large saucepan heat remaining tablespoon oil and cook the tomato mixture over medium heat for about 3 minutes. Add the chicken broth and the rest of the mushrooms. Season with salt to taste and simmer for a few minutes to let the flavors blend.
Serve immediately, garnished with epazote leaves.