Method
Heat the milk in a medium saucepan over medium heat until it reaches 180°F, stirring occasionally to prevent scorching.
Remove the saucepan from the heat and let the milk cool to 110°F. This should take about 20–30 minutes.
Once the milk reaches 110°F, whisk in the plain Greek yogurt until fully combined.
Pour the mixture into clean glass jars or a large container. Cover tightly and let sit undisturbed for 6–12 hours.
After the yogurt has set, refrigerate it for at least 2 hours before serving. Stir in honey if desired.
Notes
For a creamier texture, consider straining the yogurt after fermentation.