Mustard and Dill Herring on Pumpernickel Canapés

Ingredients

• 2 tablespoons Dijon mustard
• 1 tablespoon whole-grain mustard
• 1/2 tablespoon white wine vinegar
• 3 tablespoons extra virgin olive oil
• 1 fillet pickled herring, cut into 14-16 bite-sized pieces
• 1/2 loaf pumpernickel bread, crust removed, cut into 1/2’’-thick slices
• 3 teaspoons dill
• 2 slices red onion, cut paper thin
• Kosher salt and black pepper, to taste