Melt the butter in a saucepan over low heat. When the butter is melted, use a teaspoon to remove the white milk solids that have risen to the top of the pan. Decant the remaining butter into a glass container and cool to room temperature. This is clarified butter.
Sift together the flours, salt, and baking soda in a large mixing bowl
Whisk the eggs and buttermilk together until frothy. Add 4 Tbls (60 grams) of the clarified butter to the mixture and whisk until combined.
Pour the liquid mixture into the dry ingredients and whisk until combined.
Cover and chill for at least 30 minutes or up to 12 hours.
Prepare a skillet by placing it over medium heat for two minutes.
Preheat the oven to 200ºF (93ºC). Prepare an ovenproof metal or glass tray to hold the blini and a length of tin foil to cover the tray. This will prevent the blini from drying out.
Combine the remaining clarified butter with 2 Tbls (30 ml) of vegetable oil in a shallow dish. Impale the potato onto a fork, and then dip it into the oil/butter mixture. Use the potato to smear the heated skillet with the butter and oil mixture. The starch from the potato does something — I’m not sure exactly what—but it makes all the difference to how the blini land on the hot skillet. Repeat this before every batch.
Pour batter onto the skillet to form a pancake: a tablespoon will produce a nice-sized mini blini, perfect for canapé with toppings, while a ⅓ -cup (75 ml) measuring cup will yield a decent, crepe-sized pancake that is suitable for stuffing and rolling.
Watch carefully as tiny holes begin to form on the surface of the blini. After 1 minute, flip the blini over and cook for an additional minute.
Remove the finished blini to the warmed tray in the oven. You can place a tiny knob of butter between each pancake to help keep them moist and tasty.
Blini made ahead can be stored in an airtight container for up to 2 days before consuming. Reheat them in an oven…but be warned, they won’t taste nearly as nice as they do just off the skillet!