Place all ingredients in a mixing bowl with 2 pinches of salt and whisk.
When ready to bake, remove the dish from the fridge, line the pastry with greaseproof paper and fill with baking beans. Bake until the edges are golden, about 25 minutes.
Remove the greaseproof paper and baking beans, brush the dough with 1 beaten egg and bake again for 5 minutes or until the bottom looks cooked.
Remove the dish from the oven and decrease the temperature to 300° F.
Pour ¾ of the filling into the tart dish immediately, place the tart back in the oven and carefully top it up with the remaining filling. (This is to prevent it from spilling out when filled to the top after you put it back in the oven.)
Bake for about 60 minutes or until the middle doesn’t wobble when you shake the tart lightly. Let cool for 15 minutes, then trim the edge of the pastry with a sharp knife.
Cut into 6-8 pieces and serve with spicy greens, sliced duck prosciutto and a thick Dijon vinaigrette.