1 tablespoon olive oil, more as needed
1 1/4 kg whole pork loin
1 pinch salt and black pepper, to taste
1/4 teaspoon garlic powder, to taste
1 onion, chopped
230g fresh mushrooms, sliced
1/4 cup white wine
1 (400g) tin condensed cream of mushroom soup
2 tablespoons Dijon mustard
1/4 cup sour cream

Heat the olive oil in a frying pan over medium heat. Season pork loins with salt, pepper and garlic powder. Cook pork in the oil, turning until browned on all sides, 5 to 6 minutes. Remove from frying pan and set aside. In the same frying pan, cook onion and mushrooms until they brown lightly and begin to soften; 3-5 minutes.
Pour wine into slow cooker; stir in the onion and mushrooms. Place browned pork on top of the vegetables.
Combine mushroom soup, Dijon mustard and sour cream in a bowl. Spread mixture over pork. Cover slow cooker; cook on Low until pork is tender and liquids have formed a sauce; 7 to 8 hours.