Thaw the grilled vegetables according to the package instructions. Spread black olive tapenade on one side of 2 slices of white bread and on both sides of the 3rd slice. Place a slice of melted Croque Emmental Président cheese on the first slice of bread. Spread half of the vegetables on top and sprinkle with some chopped chives, and season with pepper. Top with the slice of bread spread on both sides. Place the second slice of melted Croque Emmental Président cheese. Add the remaining vegetables and chives, and season with pepper again. Close with the last slice of bread. Flatten well between your hands. Heat a little butter in a pan. Place the croque in the pan. Cover and cook for 4 minutes. Flip the croque and continue cooking for another 4 minutes. Serve immediately.