Cut the cucumber in half lengthwise and scrape out the seeds. Slice it into thin strips.
Cut the salmon into two pieces by slicing it sideways.
Combine the egg yolk and milk.
Combine the mustard, honey, vinegar, and dill in a bowl.
Mix the sauce from Step 4 with the cucumber slices.
Top one piece of salmon with the cucumbers from Step 5 and place the other piece of salmon on top to make a sandwich.
Cut the pie crust to match the size of the salmon and wrap it around.
Cut off the excess crust and coat the surface with the egg yolk. Bake in a 180°C oven for about 20 minutes.
Story Behind this Recipe
There's a food culture campaign going on at the British Embassy in Japan that I attended called "Food is GREAT: A Taste of Britain."
I think using salmon that's meant for sashimi is a good idea. If you have leftover cucumber mix, you can use it as a dressing. When wrapping the salmon with the pie crust, make sure no air gets in. Before baking it, poke it 3 or 4 times with a skewer so the air can escape. You can accompany it with salad or tartar sauce.