To clarify the butter, melt it in a small saucepan over low heat. Using a spoon, remove white foam from surface of melted butter, and discard. Allow butter to sit 15 minutes. Pour off the golden liquid, leaving the sediment in the bottom of the saucepan. Set aside.
Place buckwheat and all-purpose flours, baking powder, salt, egg, milk, and 1 tablespoon clarified butter in a large bowl; whisk until well combined.
Heat 2 tablespoons clarified butter in a large skillet over medium-low heat. Drop batter into skillet, 1 tablespoon at a time. Cook until blinis are covered with bubbles, 1 to 2 minutes. Flip; cook until brown, about 1 minute more. Repeat with remaining batter.
To serve, top blinis with the smoked salmon, 1/2 teaspoon creme fraiche, and a sprig of dill.