Mix The Butter, Chives, Tarragon, And Garlic Together In A Bowl Until Well-Blended. Place The Butter Mixture On A Large Piece Of Plastic Wrap. Wrap The Butter With The Plastic And Shape It Into A Log About 1-Inch Thick. Place The Log In The Refrigerator To Chill. Season The Beef Tenderloin Steaks With Salt And Black Pepper. Place The Dried Mushrooms In A Spice Grinder Or Food Processor. Process Until The Mushrooms Are Finely Ground. Spread Some Of The Ground Mushroom On A Plate. Press Each Steak Into The Mushroom Powder Until Well Coated, Adding More Mushroom To The Plate As Necessary. Melt About 2 Tablespoons Herb Butter In A Large Skillet Over Medium Heat. Arrange The Steaks In The Skillet And Cook Until They Start To Firm, And Are Reddish-Pink And Juicy In The Center, About 6 Minutes Per Side. An Instant-Read Thermometer Inserted Into The Center Should Read 130 Degrees F (54 Degrees C) For Medium Rare, 140 Degrees F (60 Degrees C) For Medium. Top Each Steak With 1 Teaspoon Herb Butter Before Serving.