Cut the black bread into small rectangles (two rectangles per sandwich). Then cut the Ardennes ham slices to the same dimensions (one rectangle per sandwich). Cut the smoked trout into very thin strips (one strip per sandwich).
To assemble: Place a rectangle of black bread on a plate and cover with a rectangle of ham. On the left side of the ham place a strip of trout, and on the right side spread some fromage frais seasoned with black pepper. Cover it all with the other black bread rectangle.

CHEF’S TIP
To make the mini-sandwiches crispier, flatten the bread with a roller and grill it in the oven before assembly.