Place the chicken in a large saucepan and cover with cold water. Bring to the boil, then reduce the heat and simmer for 15–20 minutes, or until cooked through.
Meanwhile, make the salsa verde. Cook the tomatillos, chillies and garlic under a preheated hot grill for 5–10 minutes, turning frequently, until softened and charred. Leave to cool slightly, then remove the blackened skin.
Remove the chicken from the pan, reserving the cooking liquid. Shred the meat with a fork, discarding the bone.
Place the salsa verde vegetables in a food processor with the coriander and a little of the reserved cooking liquid and whizz to a sauce. Season and set aside.
Mix together the shredded chicken, chorizo and crème fraîche in a bowl, then season.
Divide the chicken mixture among the tortillas, then roll up and place seam-side down in a baking dish. Scatter over the cheese and bake in the oven for 20 minutes until heated through and the cheese has melted. Drizzle over the salsa verde and serve.