In a food processor, fitted with a metal blade, combine the cheese, walnuts and cream. Puree until smooth. Season with salt and pepper. In a small saute pan, over medium heat, add the oil. When the oil is hot, add the onions and apples. Season with salt and pepper. Saute until caramelized, about 6 to 8 minutes. Remove from the heat. Stir in the vinegar, to taste, and cool completely. Spread a heaping spoonful of the cheese mixture over each toasted round of French bread. Garnish with a small pile of the apple-onion mixture and parsley.