Peel the sweet potatoes and cut into thick sticks. Put in a bowl and sprinkle olive oil and oregano.
Put the sweet potatoes in an oven tray and roast for one hour or until soft.
Pour one tablespoon of oil in a pan and fry the onion, then add rosemary and thyme.
Then add the red wine and cook for 3 more minutes or until the wine has reduced to half its volume.
Add the meat broth, ¾ cup of blackberries, already blended, 1 teaspoon of brown sugar, and season with salt and pepper. Cook for 10 minutes over medium heat until the sauce has reduced. Set aside.
Dry the pieces of steak with some paper towel and season with salt and pepper.
Put the meat in a pan with one tablespoon of very hot oil, for 4 minutes each side, adjusting the time according to your taste.
Before serving, heat the sauce a bit and add the remaining ¼ cup of blackberries. Cook for 1 minute and mix well.
Place the sweet potato sticks in a plate, then the steak, and finally the blackberry reduction over the meat.