Whisk one egg with salt. Mix mayonnaise and sour cream (you don't have to add mayonnaise, though it does add to softness. Whisk again.
Pour the milk, whisk it. Pour melted butter afterward, mix it.
Strew buckwheat and wheat flour. Mix thoroughly, so there aren't any clots left. Leave the dough for at least 10 minutes. Buckwheat flour requires some time to swell. The density of the dough should be like that of sour cream.
Bake over medium heat. If pancakes are burning, bake them on butter.
Put fried eggs, leek, and smoked mackerel on the pancakes. (You can always change flavorings to your liking, or taste the pancakes with just sour cream).