1. For the cucumber sandwiches: peel and finely slice the cucumber then transfer to a large bowl and toss with the salt. Leave to stand for 20 minutes then pour off any water that has gathered in the bowl. Place the cucumber between several sheets of kitchen paper to remove the excess moisture. Spread the bread lightly with butter, divide the cucumber over 4 slices and season with pepper then top with the remaining bread. Cut off the crusts and cut each sandwich into 4 triangles.
2. For the smoked salmon sandwiches: roughly chop 100g of the smoked salmon and put into a small food processor with the soft cheese, lemon zest and juice then blend until smooth. Tip into a bowl, stir through the chives and season with white pepper.
3. Spread 4 slices of the bread with the smoked salmon mixture then top with the remaining smoked salmon slices. Top with the remaining slices of bread then cut off the crusts and cut each sandwich into 4 triangles.