Now this tart is the sort of thing I have dreams about - is that terribly sad? My guess is that if you are reading a blog on egg cookery you will have more than a passing interest in food and will therefore understand! It is one of those rare things that comprises a mere handful of ingredients yet the end result tastes hugely complex. I would go as far as to say this is a fairly frugal dish, albeit one of the best sorts that take a very cheap ingredient, onions, in bulk and add to it a little luxury in the form of double cream. The resulting tart is deeply savoury, rich and unctuous and really rather wonderful.
Makes a 25cm deep filled tart
for the pastry:
130g plain flour, fine milled '00' will give you a crisper pastry
75g unsalted butter
a few tablespoons ice cold water
fine sea salt
for the filling:
900g white onions, sliced
50g unsalted butter
splash olive oil
1 small sprig fresh rosemary, needles picked & finely chopped
200ml double cream
4 medium eggs
salt & freshly ground black pepper
What to do:
Preheat the oven to 180oC/Gas 4.
Begin by making the pastry. In a large bowl, season the flour with a little fine sea salt. Add the butter and rub into the flour, with cold fingers and a light touch, until it resembles crumbly breadcrumbs. Add just enough water to bring the pastry together in a ball. This will be something like 3 tablespoons, maybe a little more, maybe a little less. If you overdo it and it ends up a little sticky add a shake more flour. Wrap tightly in cling and chill in the fridge for 30 minutes.
Melt the butter very gently in a deep wide frying pan and add the onions, rosemary and a splash of oil. Cook as gently as possible for as long as possible, an hour would be good if you had the time. The point whole of this tart is the melting sublime onions, and this is a step that cannot, must not, be rushed. A square of greaseproof, scrunched up under a running tap then shaken, unfolded and tucked over the onions will provide a steamy cover that will prevent the onions burning.
Whilst the onions are cooking remove the pastry from the fridge. On a floured work surface, roll as thin as you dare and use to line a loose bottomed 25cm flan tin. Prick the base all over with a fork, line with baking paper and baking beans. Bake blind for 15-20 minutes, until the pastry is crisp and golden. Remove and allow to cool. Turn the oven down to 160oC.
Lightly beat the cream and milk with the eggs and season with a little salt and freshly ground black pepper. Spread the cooked onions over the pastry case and pour in the custard. Bake in the oven for around 35-40 minutes or until the filling is just set. Allow to cool a little before serving with a crisp green salad. I actually prefer this tart at something nearing room temperature - the onions seem to take on a more complex sweet softness when served barely warm. But you can eat if hot if that is what you fancy. I wouldn't, however, eat it fridge cold - the whole subtle point of the dish would be lost.