Caramelised Onion and Gruyère Tartlets

Method

1. Heat the oven to 200°C (180°C fan). Sit the pastry cases on a dry oven tray and warm them for 3 minutes, then leave the tray on the bench while you mix. This drives off cupboard moisture and is the difference between a shell that shatters and one that bends.
2. Tip the caramelised onions into a bowl. If liquid has pooled in the jar, drain it off. Water is the only real enemy here, and it softens pastry from the inside within the hour.
3. Stir in the caramelised onion paste, the thyme leaves and plenty of black pepper. Taste it. It should read sweet first and savoury after, and it should hold its shape on the spoon rather than slump off it.
4. Smear about a quarter teaspoon of Dijon across the base of each case. Under this much sweet onion, mustard is what stops the whole thing tasting like jam on a biscuit.
5. Spoon a heaped teaspoon of the onion mixture into each case, mounded rather than levelled. Twenty-four cases will take a little under 200g.
6. Cover the top with grated Gruyère, a heaped teaspoon each, and push it right out to the rim. The cheese that touches the edge of the pastry is the cheese that browns, and that browned frill is the best part of eating one.
7. Bake for 6 to 8 minutes, until the cheese has melted and coloured at the edges. Start watching at five. The pastry is already cooked, so the cheese is the only thing you are waiting on and the gap between golden and leathery is short.
8. Rest the tray for 2 minutes so the cheese sets enough to hold the filling, then finish with thyme tips and, if you are using it, two or three drops of the fig and honey balsamic on each. Serve within 20 minutes.

Questions we get asked

What is caramelised onion relish, and can you make it at home?

A relish is caramelised onion taken one step on, cooked out with vinegar and a little sugar so it keeps and behaves as a condiment. To make about 400g: slice 1kg of brown onions thinly, cook them in butter over low heat for 40 minutes until bronze and sticky, then stir in 2 tablespoons of brown sugar and 60ml of red wine vinegar and cook for 10 minutes more. Cool, jar, and use it within two weeks from the fridge.

What cheese melts best in a tartlet?

Gruyère, and it comes down to fat and moisture: it flows smoothly and browns without splitting into oil. Comté and raclette behave the same way. A well-aged cheddar works if you grate it finely and use a little less, since it can go greasy. Skip feta and haloumi, which soften but never flow, and skip fresh mozzarella, which releases water straight into the case.

Can you make onion tartlets the day before?

Make the filling the day before, not the tartlets. The onion mixture keeps three days in the fridge and improves overnight. Baked tartlets are at their best within the hour, though they come back reasonably well with four minutes at 180°C. The one thing that does not survive is a filled, unbaked case left out: the pastry draws moisture from the onion and goes soft.

The whole recipe rests on a shell you did not have to make, so it is worth buying the right one. The 37mm savoury minis used here sit in our tarts and pastry shells range alongside four other sizes, every one of them $9.95 a pack and baked ready to fill, and the Confiletas range covers the sweet cases if dessert is the next problem. Shipping is free Australia-wide on orders over $100, and orders placed before 12pm on a weekday are dispatched from Geelong the same day.