1. Preheat the oven to 200°C / 400°F. Line a baking sheet with parchment paper.

2. Wash and peel the potatoes, then slice them into thin rounds using a mandoline or sharp knife. Soak the slices in cold water for 30 minutes to remove excess starch. Drain the potatoes and pat them dry with paper towels.

3. In a bowl, combine salt, pepper, and truffle oil. Add the potato slices and toss to coat them evenly. Arrange the potato slices on the prepared baking sheet in a rose pattern, overlapping them slightly.

4. Drizzle melted butter over the potatoes and bake in the preheated oven for 20-25 minutes, or until crispy and golden brown.

5. Season the beef tenderloin with salt and pepper. Heat a skillet over medium-high heat and sear the beef tenderloin for 2-3 minutes per side, or until cooked to your liking. Let the beef rest for 5 minutes before slicing it thinly.

6. Assemble the dish by placing a slice of beef tenderloin on each plate, followed by a spoonful of bearnaise sauce and a potato rose. Serve immediately.