Let the steak sit out a room temperature for at least 20 minutes.
Preheat oven to broil on HIGH.
Slice the bread into twelve 1/2" thick slices. Brush or drizzle both sides of the bread with olive oil.
Toast for 2-3 minutes on each side. Keep an eye on it to ensure it doesn't burn. While still warm, rub the bread slices with the garlic cloves.
Heat up a cast iron skillet over medium-high heat until hot, about 4-5 minutes.
Season both sides of the steak with salt.
Add 1 tbsp olive oil to the skillet, then carefully add the steak.
Cook for 3-5 minutes on each side, or until desired doneness.
Let the steak rest for at least 3-5 minutes before slicing into 12 thick slices.
In the meantime, mix together all the sauce ingredients until well-combined.
To assemble, add a slice of the steak onto each crostini, then a generous dollop of the sauce. Garnish with freshly chopped chives and crushed black pepper. Serve immediately while warm. Enjoy!