Chicken with creamy mushroom sauce

Name: Chicken with creamy mushroom sauce
Ingredients: 2 tbsp unsalted butter; 3 tbsp olive oil; 350g/12oz chestnut mushrooms, thinly sliced; 1 brown onion, finely chopped; 2 garlic cloves, crushed; 1 tbsp fresh thyme leaves; 1 tsp ground coriander; 1 tsp ground cumin; 100ml/3½fl oz dry white wine; 300ml/10fl oz chicken stock; 150ml/¼ pint double cream; 100g/3½oz crème fraîche; 1 tbsp Dijon mustard; small handful fresh flatleaf parsley leaves, finely chopped; small handful fresh tarragon leaves, finely chopped; 4 chicken breasts, skin on; sea salt and black pepper; cooked white rice, to serve; tenderstem broccoli, to serve