Jacques Reymond has two methods for caramelising onions. "The first way is to thinly slice and cook down the onions in a saucepan or flameproof casserole until rich, deep and caramelised. This is the best method for an onion soup," he says. The second is to bake the onions whole. "The process of roasting lets the onion's natural sugars caramelise in the skins, resulting in a soft, sweet onion. Whole caramelised onions are great served with roasted meats, such as lamb, beef or chicken."
The process of caramelisation is what gives these onions their deep golden colour and sweet flavour. Caramelised onions also go well in a quiche – try pairing them with goat's cheese and thyme – or as a topping for a crisp puff-pastry tart with anchovies and black olives (known as pissaladière). They also work well combined with wine or beer as a rich foundation for a stew, and of course, they're the start of the show in a French onion soup.
The stovetop method
1 To caramelise onions on the stovetop, peel, halve and thinly slice 4 large brown onions.
2Heat a heavy-based saucepan or casserole over low-medium heat. Add onion, reduce heat to low and cook, stirring frequently, until onion starts to turn golden (30 minutes; this is when the natural sugar and water content has been extracted).
3 Add 100gm butter and 50ml extra-virgin olive oil, increase heat to low-medium and cook, stirring constantly to prevent burning, until fully caramelised (20 minutes). Makes about 1 cup.
The oven method
1Preheat oven to 160°C. Line a roasting tray with aluminium foil and top with a 2cm-thick layer of coarse rock salt.
2 Place large whole unpeeled white onions (brown onions don't work as well using this technique) on the salt and bake until onions are very soft when pierced with a skewer, and the caramelised juices are seeping through the skin (at least 1 hour).
A recipe for French onion soup
1 Make caramelised onion as per stovetop method, adding 1 tbsp Dijon mustard and 5 crushed garlic cloves with butter and olive oil in Step 3. Add 300ml dry white wine, 3 fresh bay leaves, 4 thyme sprigs and 3 parsley sprigs, and cook over medium heat until wine is reduced by half (5 minutes).
2 Add 1.5 litres chicken stock, season to taste and simmer over low heat for 30 minutes (do not boil).
3 Preheat oven grill to high. Remove herbs and ladle soup into flameproof bowls. Top soup with toasted sliced baguette, fitting slices to cover soup. Sprinkle with 250gm thinly sliced Comté. Grill until cheese is bubbling and golden (4-5 minutes). Season to taste and sprinkle with extra thyme leaves to serve.