A bright and pure strawberry ice cream. Buttermilk draws out the true flavor of fresh strawberries. When Ohio strawberries are at their peak, we buy up thousands of pounds per week from neighboring farms. We quickly wash, hull, and freeze them-so we can make strawberry ice cream all summer long. The best strawberries are juicy, fragrant, and sweet but have a tart edge. Roasting them for just a few minutes evaporates some of the water and concentrates the flavor. A touch of lemon juice and buttermilk helps draw out the subtle tartness of the berries. We never put pieces of strawberries in ice cream; because of their high water content, they freeze into rock-hard, flavorless chunks. Instead, we puree the berries to flavor the ice cream. You will have extra roasted strawberry puree (it's necessary to fill the baking dish with berries so they don't scorch or dry out as they roast), but you can serve it over other ice creams.
Puree the berries in a food processor with the lemon juice. Measure 1/2 cup of the pureed berries; refrigerate the rest of the puree for another use.
For the ice cream base:
Mix about 2 tablespoons of the milk with the cornstarch in a small bowl to make a smooth slurry. Whisk the cream cheese and salt in a medium bowl until smooth. Fill a large bowl with ice and water.
Gradually whisk the hot milk mixture into the cream cheese until smooth. Add the reserved 1/2 cup strawberry puree and the buttermilk and blend well. Pour the mixture into a 1-gallon Ziploc freezer bag and submerge the sealed bag in the ice bath. Let stand, adding more ice as necessary, until cold, about 30 minutes.
Pour the ice cream base into the frozen canister and spin until thick and creamy.
Pack the ice cream into a storage container, press a sheet of parchment directly against the surface, and seal with an airtight lid. Freeze in the coldest part of your freezer until firm, at least 4 hours.