For the stew, preheat the oven to 120C/250F/Gas ½. Season the lamb with salt and pepper and dust with the gluten free flour.
Heat a heavy-bottom casserole dish until hot, add the olive oil and lactose free butter then add the lamb and fry on each side until golden-brown.
Remove the lamb and keep to one side. Reduce the heat and add the carrots and celery and fry until caramelised. Add the wine and simmer until the volume of liquid has reduced by half, then add the lamb, tomatoes and the low FODMAP stock.
Bring the stew back up to a simmer then add the bay leaf and rosemary. Cover with a lid, transfer the pan to the oven and bake for one hour.
For the dumplings, mix the gluten free flour, suet, baking powder and a pinch of salt in a bowl.
Add the rosemary to the gluten free flour mixture. Gradually add small amounts of cold water, 3-5 tablespoons, or enough to form a sticky dough.
Flour your hands and then roll the dough into 12 little balls. Place on a plate in the fridge to chill. When the lamb stew is ready, place the 500ml/18fl oz lamb stock into a pan and bring to a simmer.
Add the dumplings and simmer for 6-8 minutes. Remove the dumplings and set aside to rest for a minute, discarding the cooking stock.
To serve, when the lamb is ready, remove the lid and add the dumplings and parsley to the casserole dish, then serve in a shallow bowl.