Season the bison ribeye steaks on both sides with salt and pepper. Allow to come to room temperature over 15 minutes.

In a large bowl, toss the arugula with the vinegar until completely coated then set aside.

Heat the vegetable oil in a skillet over medium-high heat. Add the butter and gently stir until the butter is melted.

Sear the steaks on both sides until rare – about 2-3 minutes per side. Remove from the skillet and allow the steaks to rest for 15 minutes. Slice thinly against the grain.

On each slice of ciabatta, spread about 1 tablespoon of mayonnaise. Then on each slice that will be a bottom half, flip it over and spread an additional tablespoon of horseradish so that one side has mayonnaise and the other has horseradish.

Place a slice of provolone onto the bottom slice of ciabatta, followed by slices of ribeye, some arugula, and finally the top piece of bread (mayonnaise side up).

Preheat a panini press or griddle on high heat and spray with cooking oil. Place each sandwich onto the griddle and press lightly until the cheese is melted – about 5-8 minutes per sandwich. Serve warm and enjoy! Wrap leftovers in parchment paper and store in the fridge for up to 2 days.