With their rich flavour and soft, gooey texture, caramelised onions add a touch of aromatic sweetness to a variety of savoury dishes. They are often served with steak and other meat dishes, used as a base for onion soup, dips and pâte, or in delicious pastries, particularly in combination with intense cheese flavours.
Most people will already have a few onions in their pantry cupboard, and making a batch of caramelised onions is a simple and effective way of adding depth of flavour to your cooking. They are also a delicious way of adding more vegetables to your diet, with onions being a good source of Vitamin C, several B vitamins, potassium and antioxidants. That said, some recipes do use a lot of added fats and sugars and should be enjoyed in moderation.
Caramelised onions are sometimes confused with sautéed onions, but the two are actually quite different in terms of taste and texture. Sautéed onions are cooked quickly over a high heat until the outsides are just browned, giving them a lighter colour, firmer texture and more savoury flavour than caramelised onions. Caramelised onions are cooked for a long time over a medium-low to low heat, breaking down the internal structure of the onion and releasing its natural sugars, so your caramelised onions cook in their own sugary juices, giving them their distinctive sweet taste.
You can caramelise any type of onion, but for maximum sweetness, try a yellow variety that is high in natural sugars, like Vidalia or Walla Walla. Most people also add a little brown sugar and balsamic vinegar to enhance the natural sweetness of the onion. Some recipes also recommend adding salt to the mixture, as this draws all the liquid out of the onions, which makes them cook more evenly and prevents them from sticking to the pan. More liquid will mean it takes longer for the onions to cook, but this recipe is all about slow cooking, and we promise that the results will be worth it.
As we’ve already mentioned, the key to great caramelised onions is to cook them for a very long time. But just how long is long enough? In fact, the perfect timing will vary according to the size and type of onion, so the best thing is to know what to look out for. When perfectly cooked, caramelised onions should be a rich, brown colour, with a soft, slightly gooey texture, but not reduced to mush. Once your onions are cooked, you can add them to your favourite savoury dish, or store them in the refrigerator for up to four days.
Steps and Ingredients
For a recipe that makes caramelised onions the star, try this French-style recipe for caramelised onion tart, where strong cheddar cheese and herbs complement sweet onions in the perfect marriage of aromatic and savoury flavours.
To make a caramelised onion tart you will need:
For the pastry case:
1¾ cups of whole wheat flour
¾ cup of butter, chilled
1 egg yolk
2 tbsp of chilled water
For the filling:
1 cup of onion, diced
1 tbsp of balsamic vinegar
1 tbsp of brown sugar
1 tbsp of butter
1⅓ cups of strong cheddar cheese, grated
⅔ cup of cream
¼ cup of milk
Fresh thyme leaves
Salt and pepper to taste.
- To make the pastry, first preheat your oven to 355 degrees F (180 C).
- Next, combine the flour and butter until they are the consistency of breadcrumbs, either by blitzing in a food processor, or placing in a mixing bowl and rubbing between your fingers.
- Add the water and egg and pulse, or stir if mixing by hand, until the mixture forms a dough, then cover with plastic wrap and refrigerate for 30 minutes.
- When your pastry is appropriately chilled, place it on a clean, floured surface and roll it out to around 5mm thick. Take a medium tart tin and line with the pastry, running your rolling pin over the edges to trim any excess.
- Cover the pastry with baking parchment and fill with baking weights, then bake for 10 minutes. Remove the weights and parchment and bake for a further 5 minutes, until golden.
- With the pastry case cooling, you can start making your filling. Heat the butter in a frying pan, then add the onions and a pinch of salt, and cook for 10 minutes over a low heat.
- Next, add the balsamic vinegar, sugar and half of the thyme leaves, cook for an additional 10 minutes, then remove from the heat and leave to cool.
- Add the cream, milk and two of the eggs to a bowl, then separate the third egg and add the yolk to the mixture. Whisk the ingredients together and add the salt and pepper.
- Add the onion mixture to the pastry casing in an even layer, followed by the cheese, then the egg mixture, with the remaining thyme leaves sprinkled over the top.
- Put the tart back in the oven and bake for around 15 minutes, until the filling is set.
For a tasty variation on a traditional caramelised onion tart, try this simple pear tart with caramelised onions and gorgonzola. Our recipe uses a light puff pastry and the classic flavour combination of gorgonzola cheese and sweet, juicy pears, with chopped walnuts for extra crunch. Serve with a light salad for the perfect lunch or supper.