Gather the ingredients.
In a large bowl, whisk together ½ cup buckwheat flour , ⅔ cup all-purpose flour, ½ teaspoon fine salt , and 1 teaspoon instant or rapid rise yeast.
Make a well in the center and pour in 1 cup warm milk , whisking until the batter is smooth.
Cover the bowl and let the batter rise until doubled, about 1 hour.
Stir 2 tablespoons melted butter and 1 egg yolk into the batter.
In a separate bowl, whisk 1 egg white until stiff, but not dry.
Fold the whisked egg white into the batter.
Cover the bowl and let the batter stand 20 minutes.
Heat butter in a large nonstick skillet over medium heat.
Drop quarter-sized dollops of batter into the pan, being careful not to overcrowd the pan. Cook for about 1 minute or until bubbles form.
Turn and cook for about 30 additional seconds.
Remove the finished blini onto a plate and cover them with a clean kitchen towel to keep warm. Add more butter to the pan and repeat the frying process with the remaining batter.
