Chicken & mushroom puff pie

Name: Chicken & mushroom puff pie
Prep time: 45 min
Cook time: 30 min
Total time: 1 h 15 min
Cuisine: British
Ingredients: 1 tbsp vegetable oil; 8 skinless boneless chicken thighs; 8 rashers smoked streaky bacon, cut into large pieces; 1 onion, halved and sliced; 250g baby button mushrooms; handful of thyme sprigs; 2 tbsp plain flour; 400ml chicken stock; 200ml milk; 500g pack fresh puff pastry, or frozen and defrosted; 1 egg, beaten