Ask your butcher to cut the roast very thinly with a meat slicer. If that option is not available, remove the meat from the package and roll it tightly in plastic wrap. Freeze for two hours, then cut extremely thinly with your sharpest knife.

Preheat your heaviest pan. (Do not use nonstick for this. I used cast iron.) Heat the oil, then add the onion and sauté until caramelized.

If the meat from your butcher came separated by wax paper, remove the wax paper until all the meat is in a pile.

Move the onions to the side of the pan and increase heat to high. Place the meat on the hot pan and lightly press to cover the pan surface. Sprinkle salt and pepper on top. Do not touch it for two minutes, then flip over and mix it with the onions to incorporate. Cook another two to three minutes or until many pieces are nicely browned and you don’t see any more raw spots. Remove from heat.

Combine mayonnaise, garlic, scallion, water, honey, and salt.

Slice the Italian loaf into thin bias-cut slices and lightly toast in the oven or in a barely oiled nonstick skillet over medium heat. Cover each crostini with avocado slices. Add Philly steak, then drizzle with Garlic-Scallion Mayonnaise. Garnish with extra scallion pieces. Serve immediately.