Preparation Mix mustard and mayonnaise in small bowl to blend. Season to taste with salt and pepper. DO AHEAD Can be made 3 days ahead. Cover and refrigerate. Mix salmon and next 8 ingredients in medium bowl. Cover and chill until cold, at least 30 minutes. DO AHEAD Can be made 4 hours ahead. Keep refrigerated. Spread 1 tablespoon mustard mixture on 1 side of each bread slice. Cut each bread slice into 6 pieces. Divide salmon tartare mixture among bread slices. Transfer to platter and serve.
Preparation Mix mustard and mayonnaise in small bowl to blend. Season to taste with salt and pepper. DO AHEAD Can be made 3 days ahead. Cover and refrigerate. Mix salmon and next 8 ingredients in medium bowl. Cover and chill until cold, at least 30 minutes. DO AHEAD Can be made 4 hours ahead. Keep refrigerated. Spread 1 tablespoon mustard mixture on 1 side of each bread slice. Cut each bread slice into 6 pieces. Divide salmon tartare mixture among bread slices. Transfer to platter and serve.