Combine the yogurt, honey, lemon juice (if using), and blueberries in a small bowl. Stir well to combine, mashing the blueberries against the side of the bowl.

Line a rimmed baking sheet or shallow storage container with aluminum foil. Pour the yogurt mixture onto the prepared baking sheet or into the container, spreading the mixture to 1/4-inch thickness.

Sprinkle evenly with the granola, breaking apart any large clusters. Freeze for at least one hour before serving.

Store in the refrigerator until ready to serve. Just before serving, break into pieces. Return leftover pieces to the freezer. To serve, remove the pieces from freezer, and eat immediately.