Step 1: Preheat your oven to 200°C (400°F). Pat the beef roast dry with paper towels. Rub all sides of the beef with olive oil, then season generously with salt and black pepper.
Step 2: Place the seasoned beef in a roasting pan. Roast for 15 minutes at 200°C (400°F), then reduce the temperature to 175°C (350°F) and continue roasting for 45-60 minutes, or until it reaches your desired internal temperature (e.g., 130-135°F for medium-rare).
Step 3: While the beef roasts, prepare the potatoes. In a large bowl, toss the peeled and cubed potatoes with melted butter and garlic powder until evenly coated.
Step 4: About 30-40 minutes before the beef is done, add the seasoned potatoes to the roasting pan alongside the beef, or on a separate baking sheet, ensuring they are in a single layer. Roast until tender and golden brown, turning halfway through.
Step 5: Once the beef reaches the desired temperature, remove it from the oven and transfer it to a cutting board. Tent loosely with foil and let it rest for at least 15-20 minutes before carving. This is crucial for juicy roast beef.
Step 6: While the beef rests, prepare the chocolate dessert. Gently heat the cream in a small saucepan over medium heat until it just begins to simmer. Do not boil.
Step 7: Remove the cream from the heat and immediately pour it over the dark chocolate in a heatproof bowl. Let sit for 2-3 minutes, then whisk until smooth and glossy. Pour into small serving dishes and refrigerate for at least 1 hour, or until set.
Step 8: Carve the rested roast beef against the grain into desired thickness. Serve immediately with the roasted garlic potatoes and the chilled dark chocolate dessert.