Peel and dice the onions and carrots. Pour the oil into the slow cooker, turn it on HIGH. Put the carrots and onions into the slow cooker; fry for 10 minutes with the lid open.
Put the spare ribs into the slow cooker. Large chop the garlic cloves and add them into the cooker.
Peel the potatoes, wash them clean and large dice. Place in the slow cooker over the ribs.
In a medium bowl, mix together the tomato paste, sour cream, mustard, Herbes de Provence, salt and pepper. Add water and stir well.
Pour the sauce over the potatoes.
BRAISE (COOK on low) for an hour and a half. Don’t stir the ingredients – you want to preserve the layered structure of the dish. Serve sprinkled with finely chopped fresh greens (chives, parsley or dill).