You could add any veg you have lying around looking sad and lonely, or use a mix of frozen vegetables instead.
splash of olive oil
500g diced stewing beef
1 onion, sliced
5-6 carrots, chopped
3 sticks of celery, thinly sliced
1 courgette, cut into chunks
3 tbsp worcestershire sauce
200ml boiling water
3 tbsp gravy granules
half a pot of Quark (I use Sainsburys own brand)
50g butter or spread
150g plain flour
1tsp dried mixed herbs
50g dried grated hard cheese (eg Parmesan, though I use the Sainsburys Basics dried hard cheese)
Heat the olive oil in a pan and add the beef. Saute until browned then scoop out, pop in a bowl and set aside. Add the onion, carrot, celery, courgette and any other veg you want to use and saute for a few minutes until slightly softened. Add the beef back to the pan, add the worcestershire sauce and cook for a minute or two. Tip in the boiling water and simmer the ingredients for 10 minutes.
Meanwhile, cut the butter into cubes and put into a large bowl. Add the flour and rub together until they resemble breadcrumbs. If it seems a bit dry, add a tsp or two of olive oil. Mix in the herbs and dried cheese.
Returning to your simmering pan, add the gravy granules and stir until a thick gravy forms around the beef and veg. Add your Quark and stir well to combine. If it seems too runny, add a few more granules, if too thick, add a splash of water and stir well. Tip the mixture into a large ovenproof dish, top with the cheesy herby crumble mix, and bake at approx 180 degrees for 15-20 minutes until lightly browned and bubbling.
I outlined my feelings on using low fat or fat free dairy products when cooking for small children in this blog post - as always, do what you think is best. If you prefer not to use a low fat product like Quark you can substitute any full fat soft cheese product that will withstand cooking - creme fraiche, marscapone or even something like Philadelphia. For very small children, the combination of gravy granules and Parmesanalike does pack a bit too much salt, so either reduce/remove the cheese or make the filling with a low salt stock cube (like Kallo) and thicken with cornflour or thickening granules.