01 - In a medium saucepan, combine the heavy cream, whole milk, granulated sugar, and salt. Heat over medium, stirring continuously until the sugar fully dissolves and the mixture begins to steam. Do not allow it to boil.
02 - Place the egg yolks in a medium bowl and whisk briefly. Slowly drizzle approximately ½ cup of the hot cream mixture into the yolks while whisking constantly to temper them. Gradually pour the warmed yolk mixture back into the saucepan, whisking to combine.
03 - Cook over low heat, stirring constantly, until the custard thickens enough to coat the back of a spoon, approximately 5 to 7 minutes. Do not let the mixture boil.
04 - Remove the saucepan from heat. Stir in the raspberry extract, lemon extract, vanilla extract, and blue food coloring until fully incorporated and the desired shade of blue is achieved.
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 and refrigerate for at least 4 hours or overnight for best results.
06 - Process the chilled custard in an ice cream maker following the manufacturer's instructions until it reaches a thick, creamy consistency.
07 - Transfer the churned ice cream to a lidded freezer-safe container. Freeze for at least 2 hours before serving to achieve a firmer, scoopable texture.