Step 1

Break the pastry into a few chunks and put in the food processor with half the walnuts. Pulse to finely chop into the pastry, then roll out the pastry on a lightly floured surface and use to line a 23cm tart tin. Chill for 30 minutes while you get the filling ingredients ready.

Step 2

Bring a pan of salted water to the boil, add the potatoes and simmer until just tender, then drain well, and tip onto kitchen paper to dry.

Step 3

Melt the butter in a pan and fry the onions really gently until very soft. Turn up the heat to caramelise them a little, then remove from the pan to cool. Add the pears with a knob of butter, and fry over a high heat to add a little colour.

Step 4

Whisk the egg, cream, milk, thyme and some seasoning – remember the cheese adds saltiness.

Step 5

Heat oven to 200C/fan 180C/gas Line the tart tin with foil, add baking beans and cook for 15 minutes until the pastry is set and sandy in colour. Remove the foil and beans and continue baking for about 10-15 minutes, or until it is golden and cooked through. Turn down the oven to 180C/fan 160C/gas 4.

Step 6

Lift the pastry from the oven and scatter in the caramelised onions, pear chunks, cooked potatoes, remaining walnuts and most of the cheese. Pour over the egg mixture, top with remaining cheese and a little more thyme, and bake until the tart is set with just a slight wobble in the centre. Serve just warm or at room temperature.