Tenderize the loin with garlic and rosemary and put on the grill for 40 minutes. Season with salt and pepper.
While it cooks, prepare the mashed blackberries: first wash the blackberries and put them in a bowl. Blend with a hand blender and heat the mashed blackberries in a pan. Season with salt and pepper and set aside.
For the potato chips: put oil in a pot and heat to 360°F. Wash the potatoes, slice with a mandoline slicer, and fry.
Serve the loin over the mashed blackberries and arrange potato chips around.