Add all dry ingredients to a saucepan and mix well.
Slowly add water and miso or mustard, whisking well. I use a whisk and a wooden spoon to incorporate everything well. An immersion (stick) blender works well too, but make sure yours is ok for hot foods.
Continue stirring and whisking over medium heat until thick. You may want to add more water depending on how thick you want the sauce at this point. Stir in lemon juice & maple syrup at end. Taste, and adjust for salt.
Use immediately, refrigerate any leftovers. When cooled, the sauce becomes "spreadable". You can return it back to a sauce by reheating and adding more water while heating it on the stovetop. An immersion blender makes this easy. Enjoy! :)