Place shallots, carrots, and celery into a slow cooker and season with salt and pepper.
Fry lardons over low heat for 10 minutes until crisp and golden.
Remove lardons and reserve the rendered fat in a heatproof bowl.
Toss chicken pieces in seasoned flour to coat thoroughly.
Fry chicken in the bacon fat for 5 minutes per side until golden-brown.
Transfer chicken to the slow cooker and top with lardons, bay leaf, and thyme.
Sauté garlic and tomato purée in the pan for one minute.
Add wine to the pan, boil for two minutes, then stir in stock and return to a boil.
Pour the liquid mixture into the slow cooker, cover, and cook on low for six hours.
Fry mushrooms in a little fat until golden and scatter over the dish before serving.