Wrap the ribeye steak tightly in plastic wrap and place in the freezer for 30-45 minutes. This will firm up the meat, making it easier to slice. Once firm, use a very sharp knife to slice the steak as thinly as possible against the grain.

In a large skillet over medium heat, melt the butter with 1 tablespoon of olive oil. Add the sliced onions and cook, stirring occasionally, for 15-20 minutes until soft and golden brown. Remove from the skillet and set aside.

Increase the heat to medium-high. Add the remaining tablespoon of olive oil to the skillet. Add the sliced steak in a single layer and season with salt and pepper. Cook for 2-3 minutes, stirring frequently with a spatula, until the steak is browned. Be careful not to overcook.

Reduce the heat to low. Add the cooked onions back to the skillet with the steak and mix to combine. Divide the steak and onion mixture into two equal piles in the skillet. Lay 4 slices of provolone cheese over each pile and allow it to melt completely.

While the cheese is melting, lightly toast the inside of the hoagie rolls. Once the cheese is melted, place an open roll face-down over one of the piles. Slide a spatula underneath the meat and cheese and, in one motion, flip it over and into the roll. Repeat for the second sandwich and serve immediately.