Season thinly sliced beef with salt and pepper
Add 1 tablespoon of extra virgin olive oil into a large skillet and place it over medium high heat
Brown the beef and then transfer it onto a plate and set it aside
Turn your ovens broiler on
Combine 2 tablespoons of creamy horseradish and 2 tablespoons of mayonnaise in a small bowl and set aside
Cut the ciabatta in half horizontally and place the bottom half onto a large plate
Generously spread half of the horseradish mayonnaise onto each half of ciabatta
Add a layer of browned beef
Add 4 slices of sharp white cheddar over the beef
Transfer the bottom portion of the panini onto a small baking sheet and broil until the cheese has melted
Add pickled red onions
Place the top half of the ciabatta over the base of your panini and press down firmly
Cut into triangles or long slices
Serve warm with kettle chips and a pickle :)