Begin by heating the heavy cream, almond milk, and erythritol in a saucepan over medium heat. Stir continuously until the erythritol has completely dissolved.
Add the dried lavender to the mixture and simmer for about 5 minutes to infuse the cream with lavender flavor. Be careful not to let the mixture boil.
Remove the saucepan from the heat and let it steep for 15 minutes. After steeping, strain the mixture to remove the lavender, returning the liquid to the saucepan.
In a separate bowl, whisk the egg yolks. Gradually temper the yolks by adding a small amount of the warm cream mixture, whisking constantly to prevent the eggs from scrambling.
Pour the tempered yolks back into the saucepan with the rest of the cream mixture and cook over low heat until the mixture thickens enough to coat the back of a spoon.
Stir in the vanilla extract and xanthan gum until well combined, ensuring there are no lumps.
Allow the mixture to cool to room temperature, then cover and refrigerate until it's completely chilled, ideally overnight.
Once chilled, puree the blueberries using a blender or food processor until smooth.
Mix the blueberry puree into the chilled ice cream base until uniformly combined.
Churn the mixture in an ice cream maker according to the manufacturer's instructions, until it reaches a soft-serve consistency.
Transfer the ice cream to a freezer-safe container and freeze until firm, usually about 4 hours.
Before serving, let the ice cream sit at room temperature for a few minutes to soften for easier scooping.