A recipe for Caviar Sandwiches with onion and lemon

Caviar Sandwiches with onion and lemon.  Beat a quarter of a pound (± 120 g) of butter to a cream; add two tablespoonfuls of onion juice, the same of lemon, a saltspoonful of paprika, and gradually four tablespoonfuls of caviar. Spread this on thin slices of brown bread or pumpernickel, put two together, press lightly and cut into long, narrow shapes.