1-2 European cucumbers
Salt and black pepper
White wine vinegar
Pumpernickel or wheat bread very thinly sliced
Butter at room temperature

Peel a European cucumber and slice it into transparent slices with a mandolin or very thin slicer (a potato peeler works well too).

Sprinkle these thin slices with a little of white wine vinegar and salt and let drain in a sieve for about 1/2 hour. Drain away any excess water and pat dry with a paper towel.

Cover a slice of lightly buttered thin brown bread with 2 layers of cucumber and a bit of black pepper and top with another slice of buttered bread. Press firmly with the palm of your hand.

Cut off the crusts. Cut into small rectangles or triangles. Cover with plastic wrap until served.

Source: Celestial Seasonings