Preheat the oven to 400°F (200°C).

Wrap the potatoes individually in aluminum foil.

Bake the wrapped potatoes for 1 hour, or until they are soft when pierced with a fork.

While the potatoes are baking, bring a pot of salted water to a boil.

Add the chicken fillets to the boiling water and cook for approximately 12 minutes, or until cooked through.

Remove the chicken from the water and let it cool slightly.

Cut the cooked chicken into small, bite-sized pieces.

In a bowl, combine the chopped chicken, pineapple cubes, sliced red onions, and marjoram.

Add mayonnaise and mascarpone to the chicken mixture.

Season the mixture with curry powder and brandy.

Adjust seasoning to your preference with salt and pepper.

Once the potatoes are baked, carefully unwrap them.

Cut each potato open lengthwise.

Fill each opened potato with the chicken curry mixture.

Serve the filled potatoes on a bed of oak leaf lettuce.

Garnish with extra pineapple pieces and fresh marjoram sprigs.