Preheat your oven to 450F and place the top rack in the lower third of your oven. Like a baking sheet with parchment paper (optional, for easier cleanup).Wash and pat dry the leek. Slice the leek lengthwise, then cut each half into long, very thin strips.
Cut the strips into short pieces, about long. Set aside.Divide the dough into two equal parts, and roll out each into a 10 circle. Gently spread a thin layer of mascarpone on the surface of the dough, leaving at least a crust.In a small bowl, break up the smoked salmon using your fingers until it is fluffy. You want the filling of the calzone to be pretty even, or it will fall apart as you eat it.Divide the salmon between the two crusts, arranging it only on one side of the crust (in a half-moon shape), again leave at least a crust.
Sprinkle the chives and leeks over the salmon, then lightly salt and pepper. Finally, drizzle with about 1 tsp of olive oil.Fold each calzone in half, making sure that the crusts line up. Using the tines of a fork, gently press down the edge all the way around the rounded side of the calzone to seal it. Make sure you get a tight seal this will help the calzone puff up during baking.
Brush the tops of each calzone with egg white.
Bake at 450F for about 15 minutes, or until golden brown and delicious.
