Combine the flour and buckwheat flour in a bowl and whisk. Separate the egg. Add the yolk to the flour mixture and set the egg white aside in a clean bowl.
Add milk and melted butter to the flour mixture. Whisk until smooth. Season with salt and pepper and whisk briefly.
Whip the egg white until stiff peaks form. Gently fold it into the batter, keeping the mixture light and airy.
Heat a bit of vegetable oil in a skillet. Add 1 tablespoon of batter per blini. When the top starts to set, flip and cook until golden brown on both sides, about 1-2 minutes per side.
Let the blini cool before topping, although some toppings taste great on warm blini! Your choice.
How to store
Keep refrigerated in an airtight container for 2-3 days or freeze them for up to 3 months.