Method
First, prepare the veg and apples; trim the onions and peel them, then cut in half and slice into thin crescents. Trim the celery sticks, then cut into 0.5cm slices, removing any tough strings as you go. Peel and core the apple, cutting it into bite-sized pieces, trim the leeks and cut into slices roughly the same as a £1 coin, then do the same with the carrots. Put your casserole dish on the hob, over a medium heat, then add the sunflower oil, onions, celery, bay leaves and thyme, and cook for 6-8 minutes until the vegetables are starting to soften. Add the pork to the dish and cook for 3-5 minutes, stirring occasionally, until the meat changes colour all over - it doesn’t need to brown, just become slightly golden at this stage. Next, add the mustard, cider and flour, then crush in the garlic. Give everything a good stir, then slowly pour in the hot stock, stirring as you go to stop lumps forming. When you have added all the stock, put the prepared apple, leeks and carrots into the dish and season to taste with salt and pepper. Increase the heat and bring the liquid up to the boil, then reduce to a simmer and put the lid on the dish. Simmer for about an hour, stirring every so often, until the meat and vegetables are tender and cooked through. After the stew has had half an hour of its cooking time, switch your oven on to preheat to 190°C (Gas Mark 5). Make the dumplings by putting the flour and baking powder into a mixing bowl and giving them a quick whisk to remove any lumps, then finely chop the sage leaves and add them to the bowl, together with a pinch of salt and a few turns of the pepper mill. Put the yogurt into a measuring jug and make up to 100ml with cold water, then stir in the oil. Pour this liquid into the flour and stir in gently to make a soft dough (it will be slightly sticky). Take the lid off the casserole dish and set aside, then lightly flour your hands, divide the dough into eight roughly equal pieces and roll them into balls. Drop the balls carefully on top of the stew, drizzling each one with a little oil. Put the casserole dish in the oven (leave the lid off) and cook for 15-20 minutes, or until the dumplings have turned golden, then dish up into four bowls and serve straight away.