Chicken and kale stew with butter bean mash

Name: Chicken and kale stew with butter bean mash
Ingredients: dash oil; 1 butternut squash, peeled and cut into 2cm/1in cubes; 2 celery stalks, roughly chopped; 1 medium onion, finely chopped; 4 garlic cloves, finely chopped; 1 tbsp plain flour; 4 chicken thighs, boneless and skinless; 400g tin green lentils, drained; 800ml/1½ pint chicken stock (made with stock cubes); 2 dried bay leaves; 4 sprigs fresh thyme, plus extra for garnish; 1 handful finely chopped fresh parsley, plus extra for garnish; 2 tsp mustard; 80g/3oz kale, roughly chopped; salt and freshly ground black pepper; 700g/1lb 9oz Maris Piper potatoes, peeled and cut into 2cm/1in pieces; 400g tin butter beans; splash full-fat milk, if needed to loosen; olive oil, to taste