Easy tarragon chicken

Name: Easy tarragon chicken recipe
Prep time: 30 mins
Cook time: 15 mins
Yield: Serves 4
Ingredients: 50g butter; 1tbsp olive oil; 1.3kg free-range chicken, jointed, or chicken pieces; 1-2 small onions or shallots, finely sliced; 120ml dry white wine; Several sprigs of tarragon; 20g butter; Handful freshly chopped mixed herbs (such as parsley, tarragon, sorrel, chervil, dill); 1 lovage leaf; 1 shoot each of thyme and winter savory (optional); 175ml double cream (optional)