Add the milk, all-purpose and buckwheat flours, eggs and a pinch of salt to a high-powered blender and blend until thoroughly mixed.
Place a medium nonstick pan over medium heat and spray with nonstick spray. Pour about 1/2 cup batter into the preheated pan and swirl to thoroughly coat the pan with the batter, making a crepe. Cook until it has golden brown spots and edges, about 2 minutes. Flip onto a cutting board to let cool. Continue to cook in batches, covering the finished crepes with a towel to keep them from drying out.
Season the creme fraiche with salt and pepper in a medium bowl and stir to combine. Cover with plastic wrap and use a smoking gun to smoke the creme fraiche for 10 minutes.
For serving: Fold the crepes into quarters and add to a serving dish. Top with the caviar and smoked creme fraiche.