When the buckwheat is soft enough you should be able to squish the grains between your fingers. Drain into a fine mesh sieve and rinse under a tap. Place the sieve over a bowl and leave any excess water to drain while you prepare the remaining ingredients.
Place the chopped apple, apple juice, the cinnamon and 1 tbs of the maple syrup into a blender. Add the drained buckwheat and blend until smooth, adding more apple juice as needed to assist with the blending. Taste and add more maple syrup as needed.
Divide the buckwheat bircher muesli between 2 bowls (it might stretch to 3 depending on how hungry people are) and top with your favourite garnishes.