To make the peach puree, peel peaches and remove the pits. Cut into large pieces and blend with an immersion or countertop blender until smooth.
1 cup peach puree (approximately 3 peaches)
In a 4-quart saucepan, combine the 2 cups milk, heavy cream, prepared peach puree, sugar, corn syrup, and salt. Whisk to combine and place over medium heat.
2 cups + 2 tablespoons whole milk, 1 ¼ cups heavy cream, ¾ cup granulated sugar, 2 tablespoons light corn syrup, 1 teaspoon kosher salt
While the milk mixture is heating, in a separate bowl, combine the reserved 2 tablespoons milk and cornstarch. Whisk together until smooth.
Bring the milk mixture to a rolling boil and continue to boil for 1 minute. Remove from the heat and slowly whisk in the cornstarch slurry. Return to heat and bring back to a rolling boil. It is essential that the mixture comes back to a rolling boil to activate the thickener.
Remove from the heat, add the vanilla extract and rosemary sprigs. Stir to combine and steep for 20 minutes.
1 teaspoon vanilla extract, 2 small sprigs fresh rosemary
Once steeped, remove the rosemary sprigs and pour the ice cream base into an airtight container. Cover and chill for 6-8 hours. The ice cream base can be stored for up to 48 hours.
Once ready to chill, follow the manufacturer’s instructions with the ice cream maker. Churn for approximately 25 minutes. Enjoy immediately as soft serve, or pour into an airtight container and place in the freezer for 4-6 hours for a hard serve.