Steak Sandwich Recipe

Preheat and season

Preheat oven or fryer according to waffle fries package if using frozen; if using fresh fries, preheat oven to 425°F (220°C). Season ribeye on both sides with 1 1/2 tsp salt and 1 tsp freshly ground black pepper; let sit at room temperature for 20 minutes while you prepare other components.

Cook waffle fries according to package or recipe until golden and crispy (usually 18–25 minutes in a 425°F oven, flipping halfway). Keep warm in a low oven (200°F/95°C) while finishing sandwich components.

Heat 1 tbsp olive oil and 1 tbsp butter in a medium skillet over medium-low heat. Add the thinly sliced onion and a pinch of salt, stirring to coat.

Cook onions slowly, stirring every 3–5 minutes, for 20–30 minutes until soft and deeply golden. If they begin to stick or brown too quickly, reduce heat. Stir in 1/2 tsp brown sugar and 1 tsp balsamic vinegar during the last 2–3 minutes to boost color and flavor. Keep warm.

Heat a heavy skillet (cast iron preferred) over high heat until very hot, about 3–5 minutes. Add 1 tbsp olive oil and swirl to coat.

Place the ribeye in the skillet and sear without moving for 2.5–3 minutes to develop a deep brown crust. Flip and reduce heat to medium-high; add 1 tbsp butter and baste the top of the steak with the melted butter for another 2.5–3 minutes for medium-rare (internal temp ~130°F/54°C). Adjust time 1–2 minutes more for medium.

Remove steak to a cutting board, tent loosely with foil, and rest for 5–7 minutes. Reserve skillet drippings for optional pan sauce.

With skillet still over medium heat, add 1/4 cup beef stock to deglaze, scraping up browned bits. Simmer 1–2 minutes, then whisk in 1 tbsp cold butter to slightly thicken and gloss the sauce. Spoon a small amount over sliced steak before assembling (optional).

Slice the rested ribeye thinly against the grain into 1/4-inch slices.

If desired, toast the sandwich rolls cut-side down in a dry skillet or under broiler until lightly golden, about 1–2 minutes.

Spread mayonnaise (about 1 tbsp per roll half) on the inside of the toasted rolls if using. Layer a handful (about 1/2 cup) of baby spinach on the bottom half.

Arrange sliced ribeye over the spinach. Spoon warm caramelized onions (about 1/2 of prepared onions) over the steak.

Crumble blue cheese (about 1.5 oz) over the warm steak and onions so it softens slightly. Add the remaining caramelized onions on top if desired.

Close the sandwich, press gently, and serve with waffle fries on the side. Optionally serve extra blue cheese or pan sauce for dipping or drizzling.