Juice blood oranges and set juice aside for crêpe batter.
Using a food processor or hand mixer, beat aquafaba until fluffy and stiff. The aquafaba will turn white in color and should stop flowing at all or flow very slowly out of the bowl. Set aside for the batter.
Combine all ingredients for the crêpe batter, including blood orange juice and whipped aquafaba in a bowl. Stir just until the batter is well blended. Do not stir too long or the batter will lose its airiness. The batter is relatively runny, but that is ok.
Heat cast iron skillet to medium heat and grease well with butter/margarine.
Pour 1 to 2 ladles maximum - depends on the size of the ladle, mine is rather small - of batter into the pan. Immediately pick up the pan and swirl it so that the batter is spread thinly in the pan. You really need to work quickly here, as the batter thickens fairly quickly in the pan. Once you have the batter spread all over and a nice round crêpe, return pan to the heat.
Bake crêpes over medium heat until done. Wait to flip until crêpe bubbles appear on surface and pop into holes. Once you can run a spatula under the crêpe well without breaking the batter, you can turn the crêpe. This will take a good 2-4 minutes, depending on your stove. For the first crêpe, possibly even a little longer. On the side that is already fried, the crêpe should be golden brown. If it gets too dark, reduce stove temperature slightly.
Bake crêpe on the other side for another 2-3 minutes. Crêpe is done when it can be flipped back and forth in the pan.
Fold finished crêpe into a half-moon directly in the pan, then form the half-moon into a quarter again.
Transfer crêpe to a plate and keep warm in the oven at 50° Celsius.
Grease the pan again with butter/margarine and do exactly the same with the remaining crêpe batter until all the batter is used up. Enough for about 4 crêpes. If you have a smaller pan, maybe even for 6-8 crêpes.
Fillet the remaining two blood oranges. To do this, remove peel generously so that there is no white skin left. Cut the blood oranges along the seams/scars with a knife and then carefully remove the individual blood orange fillets.
Arrange the crêpes on plates, drape the blood orange fillets nicely on top and drizzle the orange butter over them with a teaspoon. Serve immediately.