In a small bowl, combine the softened butter, chopped tarragon, chopped chives, and lemon juice. Mix until well combined and season with salt and pepper to taste. Transfer the butter mixture onto a piece of plastic wrap, shape it into a log, and refrigerate until firm.

Remove the filet mignon from the refrigerator and let it come to room temperature for about 30 minutes. Season both sides generously with salt, black pepper, and garlic powder (if using).

Heat 1 tablespoon of olive oil in a skillet over medium-high heat. Add the green onions and cook for 2-3 minutes, turning occasionally until charred and tender. Remove from the skillet and set aside.

In the same skillet, add the remaining tablespoon of olive oil. Once hot, carefully add the seasoned filet mignon. Sear for about 4-5 minutes on each side for medium-rare, or until your desired doneness is reached.

During the last minute of cooking, sprinkle the chopped sage over the filets, allowing it to cook slightly in the residual heat.

Once cooked to your liking, remove the filets from the skillet and let them rest for 5 minutes.

Slice the chilled tarragon chive butter into rounds and place a piece on top of each filet mignon. Serve with the charred green onions on the side.