This is a delicious tart. If you are worried about making your own pastry by all means buy shortcrust pastry. Most bags of spinach are pre-washed but if yours is not, do make sure that you dry it really well before chopping (wrap in a teatowel or use kitchen paper). Tarts of any description cook better in a metal tin rather than china if you have both to hand. Do let it cool a little before serving as it will be much easier to slice.

Serves 4 – 6

3 medium onions, finely sliced
90g. / 3ozs. butter
1 ½ tsps. Salt
1 tbsp brown sugar
Black pepper
100g. / 3ozs. spinach leaves
175g. / 6ozs. blue cheese (Shropshire Blue))
1 tub mascarpone or full fat cream cheese
2 eggs, beaten
24cm. / 9 ½ inch shortcrust pastry case baked blind
Shortcrust Pastry:
175g. / 6ozs. plain flour, sifted
A good pinch of salt
90g. / 3ozs. very cold butter, cubed
1 egg yolk plus 1 tbsp. cold water
baking beans for blind baking

Make the pastry. Put the flour and salt in a food processor and aerate with a couple of quick on/off pulses. Add the butter and process until the mixture resembles fine breadcrumbs. Add the yolk and water (if necessary) and process until the pastry just draws together. Turn on to a lightly floured work surface and knead briefly. Roll out to line the tart tin and put in the fridge for half an hour. Bake blind until a good colour.
Make the caramelised onions. Melt the butter in a frying pan over a low heat, stir in the onions, sprinkle with the salt and sugar and cook gently, stirring occasionally, until meltingly soft and deep golden, about 30 minutes. Season to taste.
Meanwhile, prepare the spinach by stripping the leaves of their stalks, then rolling up the leaves and slicing them into thin strips. Mix together the blue cheese, mascarpone and egg till fairly smooth (this can be done in a food processor).
Spread the caramelised onions in an even layer over the pastry case, then press the spinach gently on top, and pour over the mascarpone mixture. Try to spread the mixture evenly over the tart so that the spinach is well covered. Bake until puffed and golden at 190C / Gas Mark 5. Serve warm cut into slices with new potatoes and a salad.