Put the flour, butter and salt in the bowl of a food processor and pulse until the mixture resembles bread crumbs. Whisk the egg lightly then, with the machine running, pour into the flour. Process until the dough begins to come together, then pour out onto the bench, knead together into a dough, wrap in clingfilm and allow to rest in the fridge for 20 minutes.

After the dough has rested, heat the oven to 200°C / 400°F. On a well floured bench roll out the dough then use it to line a 26cm tart or cake tin. Line with baking paper and weights (such as dried beans) then blind bake in the oven for 10 minutes.

Meanwhile, melt the butter in a large pan over a medium high heat. Sauté the onion until softened but not browned. Add the garlic to the pan and allow to cook gently. Remove the leaves from the chard stems and slice finely, then add to the pan with the onion and garlic, cooking until the leaves have collapsed and softened. Slice the stems thinly, lengthways and place on top of the mixture in the pan to soften slightly, before turning off the heat.

After the 10 minutes is up, remove the beans and baking paper from the pastry case, and continue to cook the pastry for 5 minutes. Remove from the oven, turn the heat down to 180°C / 350°F and set aside.

In a mixing bowl, whisk together the crumbled feta, eggs, crème fraîche and paprika together. Season well with nutmeg, salt and pepper.

Transfer the chard mixture to the pastry case (reserving the long stems for decoration) and smooth over evenly. Pour over the egg and crème fraîche, season again with salt and pepper, then decorate with the chard stems in circles (see pictures).

Transfer carefully to the oven and bake until puffed and golden, about 45 minutes.

Allow to cool to room temperature before slicing with a very sharp knife.