Creamy, not too sweet, and full of real strawberries and blueberries. Kind of like fresas con crema, but frozen. Don’t skip letting the fruit sit a bit first; the juices are what give you those swirls.
Whisk egg yolks, sugar, cornstarch, and salt in a large bowl until pale. Set aside.
In a saucepan, heat milk and cream over medium until steaming (not boiling).
Drizzle about ½ cup of the hot milk mixture into the yolks while whisking to temper.
Pour mixture back into the saucepan.
Cook over medium-low, stirring constantly, until thick and reaches 170–175°F (and coats the back of a spoon).
Remove from heat. Stir in vanilla. Cool slightly, then whisk in strawberry purée. Transfer mixture to refrigerator to cool completely.
Lightly mash strawberries in a separate medium bowl. Add blueberries and sugar. Stir to mix well. Let sit 10 minutes to release juices.
Spoon 1–2 tablespoons custard into molds. Add a small spoonful of berry mixture then add more custard to make layers.
Use a skewer to gently drag berries downward once or twice. Don’t overmix.
Cover mold, insert sticks and freeze overnight or until set. Unmold and serve.
