Crush the garlic with a sprinkle of salt into a paste. When potatoes are baked, scoop out the filling and whilst hot, mix in with the garlic and vinegar. Slowly beat in the olive oil and keep warm. Meanwhile slice the onions thinly and put into the chicken stock, bring up to the boil. Add sausages and cook for 5-10 minutes. Take out sausages, leave stock on cooking with onions. Dry off sausages and cook over barbecue or in a griddle pan with a splash of olive oil.
Thicken sauce with corn flour and add parsley. Put potato on plates, lay 3 sausages on top and cover with sauce and serve.