1. Add 1/2 cup water to each, grapes and sugar, separately.
2. Boil grapes for 3-4 minutes, or till soft. Cool.
3. Boil sugar, water till a drop pressed between fingers feels sticky (1 thread consistency)
4. Blend grapes till smooth, sieve.
5. Add to sugar syrup, boil and simmer further for 5 minutes. Cool very well.
6. Just before serving, blend grape concentrate and milk till frothy.
7. Pour into transparent glasses.
Top with a scoop of vanilla iceream if desired. Serve immediately.