Make Goat Cheese Spread: In a small bowl, add 6 ounces goat cheese, 1-2 tablespoons prepared horseradish, 1 teaspoon dried basil leaves, and ¼ teaspoon kosher salt. Set aside.
Make Crostini: Place baguette slices on baking sheet and brush with extra virgin olive oil. Place under broiler (watch very closely)* until golden brown. Set aside.
Cook Steak: Pat 6 ounce top sirloin steak dry with clean paper towel and season generously with kosher salt and ground black pepper. Bring cast iron skillet to medium-high heat and add a tablespoon of olive oil (or avocado oil). Swirl to coat the pan. Add steak to the pan and cook 2 minutes and then flip. Continue cooking 2-3 minutes per side and flipping until the internal temperature has reached 125-130℉ (for medium-rare) using an internal meat thermometer. Or you can wait until it reaches 140℉ for a medium steak.
Rest + Slice: Once steak has reached your desired temp, remove and let rest 10 minutes. Thinly slice steak.
Assemble: Once you are ready to prepare your crostini, add some Goat Cheese Spread to a piece of crostini. Place part of a basil leaf on top and then a slice of steak. Drizzle with balsamic glaze and sprinkle with a little extra kosher salt and ground black pepper.
Make Ahead: you can make the Goat Cheese Spread and Homemade Crostini ahead of time. Place the Goat Cheese in the fridge, covered. Place the crostini in a silicone bag, seal and set out on the counter. You can also make the seared steak ahead of time, just slice and place in an airtight container and leave in the fridge until ready to use.
Sliced Steak: ensure your steak is thinly sliced so it is easier to bite through.
Internal Temp of Steak: you are going to want to ensure you use an internal meat thermometer to track the internal temperature.
Gluten-Free: to make this gluten-free use a gluten-free baguette.