Preheat the broiler.
For the harissa: Place the ginger, ground coriander, cumin, salt, garlic, thyme, chiles, red bell pepper and fresh coriander in a food processor. Blitz, and then with the motor running, add the oil in a steady thread until well combined, lighter in color and paste-like.
For the ciabatta: Mix 3 tablespoons of the harissa with the softened butter and stir well to combine. Put the ciabatta on a baking sheet and spread the harissa butter over the cut sides. Tear over the mozzarella.
Grill (broil) in the oven until the cheese has melted, approximately 5 minutes. Slice and transfer to a serving board. Sprinkle with the chives and parsley and serve.
Use the harissa immediately, or store in a sterilized jar with a layer of oil on top to seal.