How to Make It
In a blender, combine the milk with the egg yolks, salt and 1/4 cup of the Basil Pesto. Blend at high speed until combined, about 15 seconds.
In a large bowl, combine the flour with the baking powder and baking soda. Whisk in the milk mixture until smooth, and then add the 1 tablespoon of melted butter and the lemon juice.
In another bowl, beat the egg whites until stiff peaks form. Using a rubber spatula, fold the egg whites into the batter just until no streaks remain.
Set a large nonstick skillet over moderately high heat and brush lightly with melted butter. Drop slightly heaping teaspoons of batter into the skillet and cook until golden on the bottom and just set on top, about 2 minutes. Flip the blini to brown the bottoms, about 30 seconds longer. Transfer the blini to a plate and cover loosely with foil. Repeat with the remaining batter, lightly buttering the skillet as needed.
Arrange the blini on a large platter. Spoon a small dollop of crème fraîche and a little salmon caviar on each blini; alternatively, dollop a little of the remaining pesto onto each blini.