Heat a frying pan and add a little oil. Brown the meat on all sides and remove from the heat.
Meanwhile, set the slow cooker to high and add the onions, potatoes, carrots, leeks, parsnips and butternut squash.
Add the meat and pour over any remaining pan juices.
Mix all the gravy ingredients together and pour over the ingredients.
After an hour, turn the slow cooker down to low and cook for 6 hours.
After 6 hours, give the stew a stir and add the field mushrooms and canned sweetcorn or peas (or both!) and leave to cook for another hour.
To prepare the dumplings, mix together the flour, baking powder, herbs and salt and then rub in the butter. Add water to form a dough and then form into balls.
With an hour or so to go, add the dumplings to the stew, and spoon over a little gravy - by now there will be plenty more liquid in the slow cooker.
When ready to serve - you want a minimum of 8 hours, but more won't hurt, stir in some gravy granules to thicken the gravy if you wish.
Dish up and enjoy!