Mince the onion and soak in water for 5 minutes. Drain and squeeze out excess water. Chop boiled eggs into small pieces.

Mix the tartar sauce ingredients (boiled eggs, onion, sugar, mayonnaise, lemon juice, salt, and pepper) in a bowl.

Slice chicken tenderloin diagonally into bite-sized pieces and season with salt and pepper.

Prepare the batter by mixing flour, beaten egg, and water in a bowl.

Combine breadcrumbs and dried basil in a tray to make herb breadcrumbs.

Dip the chicken pieces into the batter, then coat them thoroughly with herb breadcrumbs.

Heat vegetable oil in a pot to 170°C (340°F) and fry the breaded chicken pieces for about 3 minutes until golden brown and cooked through.