French onion soup and mac and cheese meet in one pan, and honestly it is hard to believe it took this long. Sweet, jammy onions, a rich cheese sauce and a golden bubbling top, all from a single skillet.
The trick is patience with the onions. Give them a proper 20 minutes and they turn deep gold and sweet, which is what makes the whole dish taste like it simmered for hours.
It feeds a crowd, reheats well, and the oven step is just long enough to set the table.
Ingredients
- 2 tbsp butter
- 3 large yellow onions, thinly sliced
- 1 tsp sugar
- 0.5 tsp salt, plus more to taste
- 2 cloves garlic, minced
- 1 tbsp fresh thyme leaves, plus extra to serve
- 400 g (about 14 oz) elbow macaroni
- 750 ml (3 cups) beef or vegetable stock
- 250 ml (1 cup) whole milk
- 1 tbsp Dijon mustard
- 200 g (about 2 cups) grated Gruyere cheese
- 100 g (about 1 cup) grated mature cheddar
- 0.5 tsp black pepper
To finish
- 50 g (about 0.5 cup) grated Gruyere, extra
- Fresh thyme leaves, to serve
Instructions
- Caramelise the onions: Melt the butter in a large oven-safe skillet over medium heat. Add the onions, sugar and salt and cook for 18 to 20 minutes, stirring often, until deep golden and jammy. If they start to catch, add a splash of water.
- Build the base: Stir in the garlic and thyme and cook for 1 minute until fragrant. Pour in the stock and milk and bring to a gentle simmer, scraping up any browned bits from the base of the pan.
- Cook the pasta: Stir in the macaroni and Dijon mustard. Cover and cook on medium-low for 10 to 12 minutes, stirring occasionally, until the pasta is just tender and most of the liquid has been absorbed.
- Make it cheesy: Take the pan off the heat and stir in the Gruyere and cheddar a handful at a time until melted and glossy. Season with black pepper and extra salt to taste.
- Grill the top: Scatter the extra Gruyere over the top and grill under a hot grill for 2 to 3 minutes until bubbling and golden in spots. Rest for 5 minutes, scatter over fresh thyme and serve.
Storing and reheating
Cool and refrigerate in an airtight container for up to 3 days. Reheat gently with a splash of milk, stirring until creamy again. Not ideal for freezing, as the sauce can turn grainy.
Frequently asked questions
Can I make this without the oven step?
Yes, but keep the heat low and stir often so the milk does not catch. The sauce will be a little thinner than the oven-baked version.
What cheese works best here?
Cheddar gives the sharpest flavour, but a mix of cheddar and mozzarella melts more smoothly. Gruyere alone is lovely too.
Can I caramelise the onions ahead of time?
Yes. Caramelise the onions a day ahead and refrigerate them; they actually taste better the next day.
Why did my sauce go thick and grainy?
Stir in a splash of warm milk, a little at a time, until it loosens. Do not add cold milk to a hot pan or the sauce can split.
Made this? Tell us how it went