Dissolve coffee powder in 12 tbsps lukewarm water to make a decoction.
Pound cardamoms in a mortar with a pestle and add to the decoction. Let the flavour infuse.
Add 1 cup milk in a cocktail shaker alongwith some ice cubes, one part of decoction and 2 tbsps sugar syrup. Shake well. This will make frappe for one glass. Similarly make frappe for remaining three glasses
Place lots of ice cubes in a tall individual glasses and pour the frappe in each glass. Serve chilled.