Parmesal Aioli: In a medium size bowl, whisk together the mayonnaise and olive oil. Stir in the garlic paste,parmesan cheese, pepper and parsley (you should have about 1 cup). Cover; refrigerate for at least 1 hour.
Steak: Season the slices of beef tenderloin with the salt and pepper. In a large skillet, heat the oil over high heat. Add the beef and cook for one minute on each side or until browned and cooked through. Remove to warm platter. Serve immediately with aioli.