Preheat the oven to 200°C/gas mark 6

Add the sliced onions, olive oil and thyme sprigs to a large heavy duty roasting tray, season with salt and pepper and toss to combine. Cover with foil and place in the oven for 45 minutes, giving the onions a stir halfway through

After 45 minutes, remove the foil and the thyme springs. Stir and sprinkle over the sugar then roast uncovered for 15 minutes

Add the crushed garlic, stir well again and roast uncovered for a further 15 minutes

Remove the tray from the oven and place over a medium heat on the hob. Add the wine, stir well and allow to bubble briskly for a 3–4 minutes

Spoon the onion and wine mixture into a large saucepan and add the beef stock. Bring the soup to a gentle simmer and cook for 10 minutes

Meanwhile, toast the baguette slices in the oven for 10 minutes, turning them over halfway through until crisp but not too coloured

Preheat the grill its highest setting

Add the veal jus to the onion soup to taste, season with salt and pepper if required and stir well. Continue to simmer for a further 5 minutes

Ladle the soup into heatproof bowls and top each with two toasted baguette slices

Scatter over the grated Gruyère and sprinkle over a few thyme leaves. Place the bowls under the grill until the cheese is bubbling then serve immediately