Step 1: Prepare the cherry swirl. In a small saucepan, combine the pitted and halved fresh cherries with 1/2 cup granulated sugar and 1 teaspoon vanilla extract. Cook over medium heat for 8-10 minutes, stirring occasionally, until the cherries soften and release their juices, forming a syrupy sauce. Remove from heat, let cool completely, then chill in the refrigerator for at least 1 hour.
Step 2: Make the ice cream base. In a large bowl, whisk together the heavy cream, whole milk, and 3/4 cup granulated sugar until the sugar is fully dissolved. Stir in the 2 teaspoons pure vanilla extract.
Step 3: Chill the base. Cover the ice cream base and refrigerate for at least 2 hours, or preferably overnight, until thoroughly chilled. This is crucial for a creamy texture.
Step 4: Churn the ice cream. Pour the chilled ice cream base into your ice cream maker and churn according to the manufacturer's instructions, typically for 20-25 minutes, until it reaches a soft-serve consistency.
Step 5: Layer and freeze. Gently fold the chopped dark chocolate chunks (if using) into the churned vanilla ice cream. Spoon alternate layers of the churned ice cream and the chilled cherry swirl into a freezer-safe container. Use a knife to swirl gently a few times for a marbled effect.
Step 6: Harden. Press a piece of parchment paper directly onto the surface of the ice cream, then cover the container with an airtight lid. Freeze for at least 4-6 hours, or until firm, before scooping and serving.