Make the crust: Take your butter out of fridge 15-20 minutes before starting your crust: I've had great results with butter that is cool, but not quite fridge temp. Cut the butter into cubes.
Begin with your potatoes boiled, thoroughly mashed (ideally, use a ricer, but otherwise just mash really well!) and cooled to room temperature.
Add your potatoes, flour and a pinch of salt to a large mixing bowl and use a pastry cutter to thoroughly mix. You will get a sandy textured mixture.
Add 1 Tbsp of ice water and all your cubed butter and cut it in with a pastry cutter until you have a (nearly) uniform dough. Some butter pieces may still appear in the dough, that's okay! Cold butter leads to flaky pastry. Wrap your dough in plastic wrap and put it in the fridge to chill for at least two hours, or overnight.
Assemble the pie: when you're ready to assemble, line a cookie sheet with parchment paper and set it aside. Preheat the oven to 350 degrees.
Begin with: cooked and cooled short grain rice ( I prefer brown jasmine rice in this recipe!) A cooked fresh salmon fillet, cooked however you prefer: I usually saute mine with butter. Four hard-boiled eggs.
Peel and chop your onion and eggs.
Prepare a lightly floured surface and a lightly floured rolling pin. Remove your crust dough from the plastic wrap and use a bench knife to cut it in half. You may need to let the dough warm on the counter for a few minutes, just long enough to make it roll-able.
Roll out the one half of the dough to a rectangle of approximately 12 inches by 16 inches, it should be 1/4 inch thick or less. If the dough sticks to the rolling pin, sprinkle a little flour onto the dough. If the edges of the dough come out very oddly shaped, use a bench knife to trim a little excess pastry from the edges.
Transfer the crust to your baking tray. It will probably hang over the sides of the pan a little, that's okay!
Spread half of the cooled rice onto your bottom crust. Break your salmon into small pieces.
Layer on the onion, chopped eggs, and salmon. Add the remaining rice, and season with salt and white pepper or freshly cracked black pepper. Add your fresh dill.
For the top crust, take the remaining half of the dough and roll dough out to the same dimensions. Lift it gently on top of the pie fillings. Use your fingers or a fork to pinch the dough edges together.
For the egg wash, beat your egg and milk or cream in a small bowl. Use a pastry brush to brush the egg mixture over the top of the pie.
Bake for 55-65 minutes, until golden brown.
Use a large knife or a round cutter to slice the pie into squares and enjoy!