Step 1In a medium saucepan over medium heat, bring the cream, milk and salt to a bare simmer. Whisk in the green tea powder until dissolved. Meanwhile, in a medium bowl, whisk together the eggs and sugar.
Step 2Whisk 1 cup of the hot cream mixture into the egg mixture to temper the eggs, then slowly pour the eggs into the saucepan, stirring constantly with a wooden spoon. Continue to cook over medium heat, stirring constantly, until the mixture thickens to a custard (it will be thick enough to coat the back of the spoon).
Step 3Immediately remove the pan from the heat and strain the custard into a medium bowl set over a bowl of ice water. Stir the custard until it is cold.
Step 4Freeze the custard in an ice cream maker until frozen, then transfer to an airtight container and freeze until hardened.