01 - In a medium saucepan, combine the whole milk, heavy cream, granulated sugar, and salt. Set over medium heat, stirring frequently, until the mixture is steaming and the sugar has fully dissolved. Do not allow it to reach a boil.
02 - In a separate mixing bowl, whisk the egg yolks until smooth. While whisking constantly, slowly pour about ½ cup of the hot dairy mixture into the yolks to gently raise their temperature without scrambling them.
03 - Gradually pour the warmed yolk mixture back into the saucepan, whisking continuously. Cook over medium-low heat, stirring constantly with a wooden spoon or spatula, until the custard thickens enough to coat the back of a spoon, approximately 5 to 7 minutes.
04 - Remove the saucepan from the heat. Stir in the vanilla extract, raspberry extract, lemon extract, and almond extract until well combined. Add the blue food coloring, starting with 3 drops and adding more as needed, mixing until the color is even and vibrant throughout.
05 - Pour the custard through a fine-mesh sieve into a clean bowl to remove any cooked egg bits. Allow it to cool to room temperature, then cover the surface directly with plastic wrap and refrigerate for at least 3 hours or until completely chilled.
06 - Pour the chilled custard into an ice cream maker and churn according to the manufacturer's instructions until it reaches a soft-serve consistency. Transfer the churned ice cream to a freezer-safe container, cover tightly, and freeze for 1 to 2 hours until firm enough to scoop.