Add half the oil to a large hot pan.
Season the chicken pieces with salt and pepper. Add to the pan and fry until deep-golden brown, then turn over and repeat on the other side.
Heat a large casserole or heavy based pan until hot then add two tablespoons of oil. Fry the lardons until crisp, then add the shallots and garlic and cook until coloured.
Transfer the chicken to the casserole. In the same frying pan, fry the mushrooms in the butter for 3-4 minutes. Add the Madeira, stock, cream and tarragon. Season to taste with salt and freshly ground black pepper.
Pour the sauce over the chicken and simmer for 15-20 minutes.
To serve, pile the chicken in a serving bowl, cover in sauce and shave over the truffle.