01 - In a medium saucepan, combine the heavy cream, whole milk, and granulated sugar. Heat over medium heat, stirring occasionally, until the mixture is just steaming (do not boil) and the sugar has fully dissolved.
02 - In a separate mixing bowl, whisk the egg yolks thoroughly. Slowly drizzle about ½ cup of the hot cream mixture into the yolks while whisking constantly to temper them and prevent scrambling.
03 - Pour the tempered egg yolk mixture back into the saucepan. Cook over low heat, stirring constantly, until the custard thickens slightly and coats the back of a spoon, reaching 170–175°F. This should take about 5 to 7 minutes.
04 - Strain the custard through a fine-mesh sieve into a clean bowl to remove any cooked egg bits. Allow it to cool for 10 minutes at room temperature.
05 - Stir in the lemon juice, almond extract, raspberry extract, vanilla extract, and blue raspberry drink mix powder if using. Add blue food coloring a few drops at a time until the desired vibrant blue shade is achieved.
06 - Cover the bowl and refrigerate the custard for at least 4 hours, though overnight chilling will yield the best results.
07 - Pour the chilled custard into your ice cream maker and churn according to the manufacturer's instructions until it reaches a soft-serve consistency.
08 - Transfer the churned ice cream to a freezer-safe container, cover tightly, and freeze for at least 2 hours to firm up before serving.