1. Prepare the Raspberry Sauce:
In a small saucepan, combine raspberries, sugar, and lemon juice. Cook over medium heat until the raspberries break down and the mixture thickens, about 5-7 minutes.
Strain the mixture through a fine mesh sieve to remove the seeds. Let cool to room temperature.
2. Make the Ice Cream Base:
In a medium saucepan, heat the milk, cream, and half of the sugar over medium heat until warm (do not boil).
In a separate bowl, whisk the egg yolks with the remaining sugar until pale and thick. Slowly pour a small amount of the warm cream mixture into the egg yolks, whisking constantly to temper them.
Pour the tempered yolk mixture back into the saucepan. Cook over low heat, stirring constantly, until the custard thickens and coats the back of a spoon (170-175°F). Remove from heat and stir in the vanilla extract.
3. Cool and Chill:
Strain the custard through a fine sieve into a clean bowl. Let cool to room temperature, then cover and refrigerate for at least 4 hours or overnight.
4. Churn the Ice Cream:
Pour the chilled custard into an ice cream maker and churn according to the manufacturer’s instructions. During the last few minutes of churning, drizzle the raspberry sauce into the ice cream to create a swirl effect.
5. Freeze and Serve:
Transfer the ice cream to a freezer-safe container and freeze for 2-4 hours for a firmer texture. Scoop and serve with additional fresh raspberries if desired.