I used seeded dates and soaked the dates in warm water for 20 minutes. Then I removed the seeds and chopped them into small pieces. If you use deseeded and soft ones, you can skip this soaking step. Make sure to chop or tear the dates into pieces so that it doesn't get stuck in the blender blades.
Blend and make lassi -
Add the chopped dates, gulkand, yogurt, and ¼ cup of water to a blender.
Blend it thoroughly. I used my Blendtec and used the smoothie setting.
Now check the consistency and, if required, add ¼ more cup of water and blend it again.
Transfer it to glasses, garnish it with dried rose petals, and serve right away.
Notes
Adjust the amount of water as per your consistency preference. Do not add more water and make the lassi thin.
Gulkand or the rose jam contains sugar too. But the amount varies by brand. Adjust the dates and gulkand amount accordingly and to taste.