Cut the passion fruit in half and scoop out the flesh, setting it aside in a bowl. Wash and dry the passion-fruit skins and set them aside for assembling the dish.
Chop the chilli pepper and finely chop the shiso leaves.
Dice the salmon and scallops into ¼-inch (5-mm) cubes. Place in two separate bowls. Sprinkle each with the lime zest, chopped chilli pepper, and chopped shiso. Add 1 tablespoon passion fruit to each of the bowls. Fold together. Season with salt.
Fill half the passion fruit shells with the salmon tartare and the other half with the scallops. Arrange one shell of each on each plate. Garnish with a few chive flowers.