Step 1Soften gelatin in 1 cup cold milk.
Step 2Bring remaining cup milk and jaggery to boil with cardamom and zest. Remove from heat. Add softened gelatin to hot milk and stir until dissolved. Let come to room temperature, about 1 hour. Stir in yogurt. Strain through fine sieve. Pour mixture into 5 individual (4-ounce) ramekins. Chill in refrigerator until completely set, at least 4 hours.
Step 1Place water, palm sugar and lemon juice in saucepan over medium heat. Just before syrup comes to a simmer, skim off top as some impurities may rise to surface. Bring to full rolling boil, remove from heat, then cool.
Step 1To serve, dip ramekins in hot water just a few seconds to loosen panna cotta. Invert onto serving dish and remove ramekin. Pour small amount of palm sugar syrup on top of each panna cotta and surround each with lemon segments and grapes. Panna cotta will be bitter without syrup.