Bolognese Pasta Sauce

4 tablespoons butter 
1 finely chopped small onion
1 stalk celery -minced
1 finely chopped small carrot
2 ounces crisp finely chopped bacon 
1 bay leaf 
3/4 pound ground beef 
1 1/2 teaspoons sifted flour
1/2 cup dry red wine 
1/2 cup beef stock 
salt and pepper 
pinch cloves 
1/2 cup milk 
2 tablespoons cream 
1 chicken liver, minced 
1/2 ounce dried mushrooms  

Soak mushrooms for 30 minutes in hot water to cover. 
Drain liquid and filter it through cloth or a paper coffee filter to remove grit. Finely chop the mushrooms.
In a large pot melt butter and gently saute onion, celery, carrot, pancetta and bay leaf for 8 to 10 minutes. 
Add ground beef, increase the heat slightly and cook until golden brown. 
Sprinkle in flour, stir through and cook for 30 seconds before adding wine. 
Stir over a high heat until most of the wine has evaporated. 
Add mushrooms and their liquid and taste for salt before seasoning. 
Add cloves and half the stock and simmer over a low heat, covered for 1 1/2 hours.
Stir from time to time and add remaining stock. When two-thirds through add milk and adjust seasonings.
Just before serving stir in cream and chicken liver and cook, uncovered, for a minute or two.
Add a tablespoon or two of tomato paste for extra richness and color if you prefer