Preheat a fan assisted oven to 175°C.
Rub the flour, salt and the grated butter until a breadcrumb texture is achieved.
Add the egg yolk and water and mix until a soft dough is formed.
Knead the dough for a further minute. Now wrap it in cling film and chill for at least 30 minutes.
Take the pastry and roll out to around a 3mm thickness. Use this to line a quiche mould.
Leave a little over hang of pastry on the edges of the quiche mould. Place baking beans (or rice can be used instead), into parchment paper on top of the pastry.
Now bake this at 175°C for 15 mins.
Remove the pastry case from the oven. Take away the beans and parchment paper. Now brush the pastry with yolk and bake for a further 5 mins. This will help to seal the pastry. Allow the pastry to cool.
For the custard, mix all ingredients together and set aside.
For the filling, sweat the diced onion in butter, then add the fennel seeds.
Add the washed watercress, mix into the onion mix until the watercress is wilted, now add the ½ lemon zest. Remove from the heat and allow to cool.
Now add the flaked smoked trout.
To combine, add the filling, then the custard. Now grate some of the Davidstow® 18 Month Extra Mature cheddar on top.
Bake this again at 155°C for 35 mins. Allow to completely cool, before trimming the excess pastry on the edge, using a small knife.
Once completely cool, remove from the mould.