Place the flour, butter and salt into a bowl. Using your fingers, rub the flour and butter together until it resembles coarse breadcrumbs. Add 6 tablespoons of ice-cold water and mix with a knife until a dough forms. 

Transfer the dough to a lightly floured surface and knead it until smooth. This should take about two minutes.

Form the dough into a disc and wrap it in plastic wrap and refrigerate for an hour.

Boil the potato in salted water until tender, then add the green beans and cook for a minute more. Using a slotted spoon, transfer the vegetables to a bowl of ice-cold water, then drain and place in a bowl.

Add the lettuce and salmon to the vegetables and set aside. 

Blend together the milk, cream, oil, mustard, eggs, anchovy, garlic, shallot and salt and pepper until smooth and add to the vegetables and salmon. Stir to combine and place in the fridge until ready to use. Preheat the oven to 170C. 

Roll the dough into a thirty-two centimetre circle and transfer to a greased 26-cm spring-form tart tin with a removable base, pressing the dough gently into the base and sides of the tin.

Place the tin on a baking tray.  Prick the dough with a fork and cover with parchment paper and fill with dried beans. Bake until slightly firm, about 15 minutes.

Remove the paper and beans and spread the filling into the crust.

Arrange the tomatoes and olives on the top and bake at a reduced oven temperature of 150C for about 20 minutes. Let the tart cool slightly before removing from the pan to serve.

Tips

The tart holds up well for left-overs and can be made a day in advance. The beauty of a tart is that you can prepare and par-cook the tart shell in advance and the filling combinations are endless.