In a large saucepan, over medium-high, heat 2 tablespoons of the oil. When the oil is hot, add the onions, Using your hands, crush the bay leaves over the onions. Season with salt and pepper. Saute for 8 minutes. Add the sausage and continue to cook for 2 minutes. Add the garlic cloves and tomatoes. Season with salt and pepper. Saute for 2 minutes. Stir in the potatoes and herbs. Season with salt and pepper. Add the chicken stock and bring the liquid to a boil. Reduce the heat to medium and cook for 15 minutes. Toss the sardines with the remaining olive oil. Season with salt and pepper. Skewer four sardines on each wooden skewer. Place the skewers on the grill and cook for 2 minutes on each side. Remove from the grill. To serve, ladle the stew in the center of each shallow bowl. Lay one skewer of sardines over the stew and serve.