Place sandwich steaks in a nonreactive dish. Combine all marinade ingredients and pour over steaks, turning to coat.

Marinate in refrigerator for at least four to six hours, turning every few hours so the meat gets marinated evenly on all sides.

Meanwhile, place cubed potatoes in a large pot. Cover with water and add one teaspoon of salt. Bring to a boil and cook until very soft, 16–18 minutes. Drain well and return potatoes to pot. Use a potato masher to mash the potatoes until smooth.

While the potatoes are cooking, sauté onion in oil until golden. Add sautéed onions, potato starch, and 1/4 cup of oil to potatoes and mix until smooth. Season with salt to taste.

Preheat oven to 400°F (200°C). Grease or line two nine x13-inch (20×30-centimeter) baking pans.

Place three to four pepper strips across the center of each steak. Add a heaping tablespoon of mashed potatoes on top and gently shape into a log.

Roll each steak up and around the filling and secure with a toothpick. Place the steaks in the prepared pans, leaving some space between each roll-up.

Place the pans on lower oven rack. Turn oven setting to broil, and broil for 10 minutes.

Sprinkle with chopped parsley or scallions for garnish. Serve immediately.