Place buckwheat in a bowl and cover with water. Cover bowl and let sit at least 1 hour or until you can squish the grains between your fingers.
Drain water using a fine mesh sieve and rinse buckwheat. 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, cinnamon, and 1 tablespoon 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 muesli between 2 bowls (it might stretch to 3 depending on how hungry people are), and top with your favorite garnishes.