Prep the Beef: If your roast is soft, place it in the freezer for 45 minutes to make slicing easier. Trim any connective tissue or excess fat. Slice the beef against the grain into thin strips (about 1 cm thick and 2x3 inches long).
Make the Teriyaki Marinade: In a large bowl or zip-top bag, whisk together the toasted sesame seeds, dark brown sugar, soy sauce, pressed garlic, sesame oil, mirin, hoisin sauce. (Note: Do NOT add the pineapple juice yet).
Marinate the Beef: Add the sliced beef to the teriyaki marinade and toss until well combined. Cover and refrigerate for 1 hour (or up to 24 hours). If you are using wooden skewers, submerge them in water to soak while the meat marinates.
The Pineapple Tenderizer (Optional): Only do this if using a tough cut of meat! Exactly 5 to 15 minutes before you are ready to cook, pour the pineapple juice into the marinating beef and stir. Do not exceed 15 minutes or the meat will disintegrate into mush. (If using a tender cut of beef, skip this step entirely).
Skewer the Meat: Remove the beef from the fridge. Skewer about 6 - 8 beef slices onto each soaked stick, leaving a 2-inch gap at the bottom for easy handling. Place the assembled skewers on a foil-lined tray.
Thicken the Glaze: If you have excess marinade left in the bottom of the bowl, pour it into a small saucepan. Bring it to a boil over medium heat, stirring occasionally, until the sauce reduces and thickens. Use this as an extra finishing glaze!
Grill and Serve:Preheat your BBQ grill (or an indoor grill pan) to medium-high heat (approximately 400°F). Grill the skewers for 3 to 4 minutes on each side until the meat is cooked and the sauce is sticky and slightly charred. Brush with the thickened glaze from Step 6, and serve immediately!