Heat ½ tablespoon of vegan butter in a non-stick skillet over medium heat. When melted, add 1 tablespoon of coconut sugar, 1 tablespoon of cinnamon and the salt, and stir together. Add the apple slices and stir until thoroughly coated and bubbly, about 1-2 minutes. Add 1-2 tablespoons of water to keep the sugar and butter from burning. Reduce heat to medium-low, and cook, covered, stirring occasionally, until apples are tender, about 10-12 minutes.
Reserve about 18 apple slices (3 per piece of French toast) and set aside. Place the rest of the apple slices (about ¾ cup) in a blender.
To the blender with the apple slices, add the oat milk, 1 teaspoon of sugar, 1 teaspoon of cinnamon, and 2 tablespoons of flaxseed. Blend for about 30 seconds.
Pour the batter into a shallow dish and allow it to rest for about 10 minutes. (It will thicken as it rests.)
Soak 2 bread slices at a time in the batter, turning over to thoroughly saturated the bread on both sides.
Wipe the non-stick skillet clean. Heat about ½ tablespoon of vegan butter on medium heat. When the butter is hot and bubbly, add 2 soaked bread slices. Cook 3 minutes per side, on medium heat. Repeat with the remaining bread slices.
Top with reserved apple slices, and if desired, toasted walnuts, vegan butter and maple syrup.
Notes
To keep the cooked French toast warm while you prepare the rest, place them on an oven proof plate or baking sheet in a 140 degree warm oven.