Optional: salt & black pepper, a shake of Worcestershire sauce.
Dollop of Dijon mustard on each sandwich
Instructions
Cook the filling In a skillet over medium heat, cook the Steak-umm sheets. Add diced onions and cook until the onions soften and the steak browns. Season lightly if you want. Let cool slightly.
Prep the bread – Trim crusts off the white bread. Use a rolling pin or cup to flatten each slice.
Fill & seal – Add a small spoonful of steak-onion mix to the center of one slice. Top with cheddar cheese.
Place another slice on top and press edges firmly to seal (fork-crimp or pinch tight).
Oil & bake
Lightly brush both sides with oil.
Place on a parchment-lined baking sheet.
Bake at 400°F for 12–15 minutes, flipping halfway, until golden brown and crisp.
Rest & serve – Let cool 2–3 minutes so the cheese sets. Serve warm.