Heat the butter in a casserole dish set over a medium heat.
Sweat the onions for 10-12 minutes, stirring occasionally until soft. Add the sugar and continue to cook until lightly caramelised; usually 5 more minutes.
Add the stewing beef to the dish and cover with stock. Bring to the boil then reduce to a simmer for 60 minutes. Remove from the heat after 60 minutes and adjust the seasoning as necessary.
Keep covered to one side.
Cook the macaroni in a large saucepan of boiling, salted water until 'al dente'; usually 8-10 minutes. Drain and spoon onto serving plates. Top with pieces of the stewed beef and some onions from the dish. Garnish with thyme sprigs and some salt and black pepper before serving.
For top tips on protecting you and your family when preparing raw meat and poultry, visit Food Safety in the Home.