Concord Grape Ice cream-Kem nho Concord

This recipe is based on Martha Stewart's Concord grape Swirl Ice Cream.
I adjust and use less ingredients because I have a small ice cream maker.

2 cups Concord grapes, rinsed and stemmed

6 egg yolks

3/4  and 1/3 cup sugar, divided

1 cup milk

1½ cups heavy cream 

2 tsp pure vanilla extract or 1/2 vanilla bean, split and scraped.

1/4 tsp salt

1. Mash grape and 1/3 cup sugar in a medium saucepan (just to separate the skin and pulp).  Bring it to a boil over medium high heat.  Reduce heat down to simmer  until the pulp turns opaque and start to burst about 5 minutes.  Remove from heat. Strain liquid through a fine or medium mesh sieve into a bowl about 1/2 cup.  Set the sieve over another bowl and press the grapes against the sieve to separate the pulp and the skin/seeds. We should have about 1/2 cup grape mixture.  Cover and refrigerate the liquid overnight.  Spread grape mixture in a metal disk and transfer it into the freezer until firm but not solid. It took me near 6 hours.  Next time I will freeze it  overnight in an airtight container.
2. Whisk egg yolks with 6 Tbs sugar and salt in a bowl until pale yellow.  Combine milk and cream in a medium saucepan, add vanilla seeds and pot.  Bring it to a gentle boil over medium high heat. When the mixture start to rise up the side, remove from heat.  Gradually whisk 1/2 of hot milk mixture into the egg yolks mixture.  Pour egg-milk mixture back to the pan , cook over medium heat.  Stir constantly until thick enough to coat the back of the wooden spoon about 6-8 minutes. Pour custard through a fine sieve to a bowl. Stir occasionally until cool. Refrigerate overnight. 
3. Mix grape juice with custard and strain through a fine sieve again. Discard solid. 
4. Transfer custard mixture to an ice cream maker  and following the manufacture's the instruction .  When ice cream is done, transfer to a bowl and fold the grape mixture in.  Transfer ice cream to an airtight container and keep frozen until serve up to  a week.