Cut baguette into 36 slices. Place on ungreased baking sheets. Spritz with cooking spray. Sprinkle with pepper. Bake at 400° for 4-6 minutes or until lightly browned.
Meanwhile, in a small bowl, combine the sour cream, chives, horseradish and salt. Top the toasts with the beef. I prefer my beef warmed so you can either do that in the microwave or once you've topped the toasts pop them back into the oven for a minute. Add a generous dallop of the sour cream mixture on top. Sprinkle with blue cheese and additional chives.