01 - In a medium saucepan, combine whole milk, heavy cream, granulated sugar, and salt. Heat over medium heat, stirring continuously, until the mixture is steaming but not boiling.
02 - In a separate mixing bowl, whisk the egg yolks until smooth. Gradually pour 1/2 cup of the hot milk mixture into the yolks while whisking constantly to temper them and prevent curdling.
03 - Slowly pour the tempered yolk mixture back into the saucepan, whisking constantly. Cook over medium-low heat, stirring continuously, until the custard thickens and coats the back of a spoon, about 5–7 minutes.
04 - Remove the saucepan from heat. Stir in vanilla extract, raspberry extract, lemon extract, and almond extract. Add blue food coloring 3–5 drops at a time, mixing until evenly colored to your preferred intensity.
05 - Pour the custard through a fine-mesh sieve into a clean bowl to remove any cooked egg bits. Allow the custard to cool to room temperature, then cover tightly and refrigerate for at least 3 hours or until thoroughly chilled.
06 - Churn the chilled custard in an ice cream maker following the manufacturer's instructions. Transfer the soft ice cream to a freezer-safe container, cover, and freeze for 1–2 hours or until firm.