I prefer to slice the beef so that it's smaller in size and thin, two long strips so when I slice it after it's cooked, it fits the toast perfectly. It also ensures the meat is to my desired doneness.
Cut beef to the desired size.
Place beef in a plastic zipper bag.
Add garlic paste and balsamic glaze.
Marinate for 1 hour to overnight.
Grill the meat over high heat, turn after 3 minutes, cook 3 minutes, and turn one more time. Depending on the size of each piece of beef, use a thermometer and remove at 130°. for medium rare. Alternatively, you can cook tri-tip in the oven.
Rest the meat for 10 minutes, then slice it 1/2" thick.
While the meat is resting is a great time to toast the bread and make the creamy horseradish sauce.
Grab some fresh herbs and have everything ready so you can serve the appetizer as soon as it's done.
Slice the bread, brush with oil, and toast the bread in the oven on a high broil for 1 minute on each side, or in a skillet.
Place the steak on the bread, drizzle with creamy horseradish sauce, and top with herbs, salt, and pepper.