Add the flour, diced cold butter and a pinch of salt to a blender.

Pulse into a fine crumble and add the cold water. Pulse well until you get a firm dough. Add extra flour if it is too sticky.

Pour the dough onto a well floured surface and knead for a couple of minutes. Wrap it in some cling film and put it aside to rest for 30 minutes. Then roll out the dough and coat a buttered tart tin with it.

Cover the pastry in the tin with a sheet of baking paper and fill it with baking beans, weights or whatever your use to blind-bake pastry.

Put the tin in a preheated oven at 356°F (180°C) and bake for 10 minutes. Take the tin out of the hot oven and remove the baking paper and weights. Let the cooked pastry rest in its tin at room temperature until needed later. In the meantime combine the fresh cream and eggs. Season with a little pepper and salt. Mix well.

Add the horseradish paste and stir again.

Put the cream aside until later. Slice the white mushrooms and transfer them to a ceramic oven dish. Microwave the mushrooms for 6 minutes on high.

Drain the mushroom juice and transfer the cooked mushrooms to a clean and dry kitchen towel. Wrap it up tightly and squeeze out as much liquid as possible.

Layer the baked pastry with the cooked mushrooms. Sprinkle with the chopped shallot and trout fillets.

Add the fresh cream and egg mixture. Season with a little pepper.

Bake the trout quiche in the preheated oven at 356°F (180°C) for 30 minutes until the eggs and cream are set. Take the quiche out and let it rest in its tin for another 5 minutes. Cut the quiche into wedges and serve.