1Warm 2 cups of the chicken broth. Put the porcini into a heatproof bowl, add the warm stock, and let stand for 20 minutes. Transfer the porcini to a cutting board and chop. Strain the broth into a bowl and set aside.
2In a large wide pot or deep sauté pan, over medium heat, melt the butter. Add the shallots and a pinch of salt and sauté until soft, about 3 minutes. Add the porcini and cremini mushrooms and the garlic and cook, stirring, until the mushrooms are tender, about 5 minutes.
3Add the sherry and simmer for 1 minute. Stir in the flour. Slowly add the mushroom soaking liquid and the remaining 2 cups stock, stirring until combined. Reduce the heat to low and simmer, stirring occasionally, for about 20 minutes. Add the cream.
4Working in batches, puree the soup in a blender until smooth, then return the soup to the pot. Season with salt and pepper. Re-warm over low heat until warm, then serve.
From south of the border comes this spicy and hearty soup ladled over crisp tortilla strips and grated cheddar. The soup is chunky with chicken and avocado, but it's the tortillas that give it a slight thickness and a special flavor.