Hot sandwiches with tuna, horseradish and mayonnaise

Ingredients:

• 340 g canned tuna in its own juice, drain the liquid first
• 4 large pieces lightly toasted rye bread
• 8 thin slices Danish Havarti cheese
• 6 tablespoons mayonnaise
• 1/4 cup finely chopped celery
• 2 green onions, finely chopped
• 2 tbsp finely chopped parsley
• 2 tablespoons apple cider vinegar
• Coarse salt and freshly ground pepper
• 1 tbsp. mustard seeds
• 1 tbsp. peeled and chopped fresh horseradish or table horseradish
• 2 tomatoes, cut into 8 discs
• Pickled cucumbers for serving (optional)

Preparation:

1. Preheat oven to 240 degrees Celsius (450 degrees Fahrenheit). Bake on the top rack. In a large bowl, combine 4 tablespoons of mayonnaise, tuna, celery, onion, parsley, and apple cider vinegar. Mix well. Season with salt and pepper.
2. In a small bowl, combine the remaining 2 tablespoons mayonnaise, mustard seeds, and horseradish. Spread the mixture on the bread and place it on a baking sheet.
   
   Spread the tuna mixture evenly on top. Top with 1 slice of Havarti cheese, making sure to cover the tuna completely.
3. Season the tomato slices with salt and place 2 on each sandwich, topping with another slice of cheese. Bake for 5-7 minutes, until the cheese is melted. Serve the sandwiches with pickles.