Preheat the oven to 180°C.
Mix flour, salt, and sesame seeds in a bowl and make a well.
Beat butter and half the eggs, then mix into the flour to form dough.
Knead dough until smooth, wrap in film, and chill for 20 minutes.
Season salmon and bake at 180°C for 20 minutes until cooked through.
Cool the fish slightly and flake into small pieces.
Increase oven temperature to 190°C.
Line a 23cm tart tin with rolled pastry and chill for 15 minutes.
Prick base, line with foil and beans, and bake for 15 minutes.
Remove foil and beans, brush with remaining egg, and bake for 5 minutes.
Reduce oven temperature to 180°C.
Arrange salmon in the pastry case and drizzle with soy sauce.
Whisk eggs with cream and pour three quarters over the salmon.
Place pak choi on top, add remaining cream mixture, and bake for 35 minutes.