Philly BreakAway red wine vinegar small red onion very finely chopped small red bell pepper seeded and very finely chopped small garlic cloves, very finely minced finely chopped fresh flat-leaf parsley finely chopped fresh oregano leaves Red pepper flakes, to taste extra-virgin olive oil Kosher salt and freshly ground black pepper rustic baguette cut into 24 thin slices Olive oil Kosher salt and freshly ground black pepper
To make the chimichurri, in a mixing bowl, whisk together the vinegar, onion, garlic, bell pepper, parsley, oregano, and red pepper flakes to taste. Slowly pour in the oil while whisking. Set aside while you prepare the steak and crostini. (The chimichurri can be made up to 2 days in advance; store in an airtight container in the fridge. Bring to room temperature before serving.)
To make the crostini, preheat the oven to 400F. Brush both sides of each baguette slice with a little olive oil and transfer to a baking sheet big enough to hold them in one even layer. Bake, turning once, until crisp and browned, about 10 minutes. Set aside.
To make the steak, season it liberally with salt and pepper and drizzle it with olive oil. Prepare flat-top grill by brushing with olive oil. Sear the steak, turning, until nicely seared on both sides until fully cooked. Transfer to a cutting board and let rest for 10 minutes.
To serve, Toss the steak slices in a bowl with a few tbsp of the chimichurri sauce. Add a few steak pieces to the top of each crostini and transfer to a serving platter. Serve the chimichurri in a bowl on the side with a spoon so guests can add more sauce as they help themselves.