These buckwheat crepe blinis were inspired by Martha's trip to Russia.
Place both flours, milk, salt, eggs, and clarified butter in the jar of a blender. Puree until smooth.
Strain mixture through a fine mesh sieve into a mixing bowl. Cover with plastic wrap, and chill in refrigerator for 30 minutes.
Remove batter from refrigerator. Heat a 6-inch crepe pan or nonstick skillet over medium-high heat. Brush with clarified butter, and heat until very hot. Add a couple of tablespoons of batter, turning and swirling the batter in the pan to completely coat. Cook until brown on the bottom, 1 to 2 minutes. Flip crepe with a spatula, and cook until golden brown on the other side, about 1 minute. Repeat with remaining batter. As you continue, you will need to use less butter in the crepe pan.
Serve crepes with sour cream and caviar.