Food: Know your onions

Combining the savoury tang of pungent goat's cheese with the sweetness of caramel, this onion tarte tatin will set your tastebuds dancing – and asking for more

I WOULD sum up this recipe, for red-onion tarte tatin, as a winner. It really impresses guests, yet it's mostly made from store-cupboard basics – all you have to do is pick up some goat's cheese and beetroot.

The concept of a tarte tatin is a traditional favourite of restaurants: everything can be assembled, ready to go in the oven at the last minute, and the same goes for you at home. The caramel will stay fresh for a week in the fridge, or up to a month in the freezer, and the onions can be cooked the day before, enabling a quick assembly on the day of your dinner. The varied mouth-feel of the tangy soft cheese, rich sweet onions and buttery pastry cannot fail to impress, and it has the added bonus of keeping vegetarians happy.

Mastering the technique for making caramel is a good basic skill to get to grips with; it's such a simple process but the results transform desserts to another level.

RED ONION TARTE TATIN WITH GOAT'S CHEESE AND ROCKET

Serves four

For the beetroot reduction
400g raw beetroot
250g caster sugar
1 tsp arrowroot
For the tart
4 medium red onions
balsamic vinegar
125g caster sugar
25g unsalted butter
100g good-quality puff pastry
2 Capricorn goat's cheeses, cut across the equator

Start by making a beetroot reduction. Peel the beetroot and place into a juicer, process, then spoon off any thick scum from the surface of the juice.

Transfer the juice into a thick-based pan and add the sugar. Place the pan on a medium heat and slowly reduce the liquid until it thickens and becomes glossy. Do not over-reduce, as it will turn into caramel and burn.

Mix the arrowroot with a little water, then remove the sauce from the heat and add the arrowroot, mixing well. Return the pan to the heat and bring the sauce to a simmer for one minute.

Pass the finished sauce through a fine strainer, then chill in the fridge until required.

To make the tart, peel the red onions, keeping them whole and taking care not to remove the root or stem. Cut each into three equal pieces, then place on a tray and add a splash of balsamic vinegar. Set aside until needed.

Place the sugar in a thick-based pan on a medium heat until it begins to caramelise (see the Critical Points, right). Reduce the heat and wait until you smell the caramel turning slightly bitter, then remove from the heat. At this point, whisk in the butter. Take care here, as the mixture will be extremely hot. Once the butter is fully incorporated, equally divide the sugar between four blini pans.

Meanwhile, place an ovenproof frying pan on a medium heat until hot, then add a little sunflower oil. Pan-fry the onions until they begin to colour, then transfer the pan to a hot oven for around eight minutes. Remove from the oven and allow to cool. Place three pieces of onion into each of the blini pans and leave to cool.

Roll the puff pastry and cut out circles that are slightly larger than the blini pans. Place the pastry over the onions, tucking the excess pastry down the sides to create a round pillow shape – use a tablespoon to make this easier. Set aside until required.

To cook, place in a hot oven for ten to 12 minutes, or until the pastry has turned golden brown and the caramel is bubbling. Remove from the oven and allow to cool for around five minutes.

Carefully turn out the tarts on to a baking sheet and place a slice of goat's cheese in the centre of each. Put them back in the oven to reheat for two minutes. Remove, dress with rocket leaves and serve with olive oil and the beetroot reduction.

Critical points

Making caramel is an excellent basic skill to master. The secret is not to stir the sugar as it melts, as this causes clumps to form.

Start by sifting the caster sugar into the centre of the pan to make a pyramid half the diameter of the pan. The heat will slowly start to melt the sugar. The melting sugar will make the pyramid start to collapse. When this happens, give the pan a shake and allow the sugar to continue melting.

When there is more liquid than dry sugar, use a heatproof spatula to work in the rest of the sugar and break down any lumps. Keep an eye out for hot spots and use the spatula to gently push the sugar around to incorporate cool sugar into areas that are overheating. It's important not to over-stir the sugar, as this can cause the sugar to clump and appear crystallised.

For desserts, you are looking for a golden caramel colour (the colour of sesame oil is a good guide). Take care not to let it get too dark, as the caramel will taste burnt and bitter. For this recipe, though, let it darken just a little further than for desserts, as you don't want it to be too sweet.