Wash and tear all the leaves roughly. Place them in a pressure cooker along with 1/4 cup water and black pepper corn and cumin seeds.
Pressure cook for 1 whistle and switch off stove. You can also microwave it. I let it steep in the cooker itself for 1/2 hour before opening the lid. Steeping the leaves is of course optional.
Transfer the leaves along with water to a mixie jar, add powdered sugar and grind to a smooth paste.
Transfer the contents into a strainer and squeeze well to extract all the juice. Discard the solid particles in the strainer.
Wet the serving glass rim in water and dip into salt to coat the rim. Add the extracted herb juice to the glass, lemon juice, honey, dry ginger powder, black salt and fill half the glass with ice cubes.
Top with club soda and serve immediately.