||In a heated pan, add butter and the beef. Sprinkle salt and pepper; cook both sides for 3 minutes. Add more butter and sauté for 5 more minutes. Leave to rest for 5-6 minutes.
||In a bowl, pour in the cream and add the spinach and rosemary.
||Once the beef has rested, place the sweet potatoes on the top of the beef. Sprinkle salt and pepper and pour the cream mixture on to the above.
||Cover the dish with parchment paper and aluminum foil and place in the oven for 2 hours.
||Sprinkle with pecans and gruyere and return to the oven for another 15-20 minutes.