CHICKEN and MUSHROOM PIE

The BEST Chicken and Mushroom Pie, similar to pot pie but chock-full of buttery mushrooms, chicken, and cheese, all stuffed in pre-made puff pastry dough for an easy, filling, comforting dish all done in under 1 hour! Ingredients 2 tbsp olive oil 3 chicken breasts, skin and bone removed, cut into pieces 150g/5½oz button mushrooms, quartered 1 small onion, chopped 1 garlic clove, finely chopped 50g/2oz butter 2 tbsp plain flour, plus extra for dusting 300ml/½ pint milk 200ml/7fl oz chicken stock freshly grated nutmeg, to taste freshly ground white pepper pinch salt small handful fresh parsley, chopped 500g/1lb 2oz ready-made shortcrust pastry 1 free-range egg, beaten