Melt the butter in a large saucepan over medium-high heat. Add the bacon and fry until slightly crispy.

Add the onions, carrots, celery and garlic. Cook until the vegetables are soft.

Sprinkle the flour over the vegetables and stir well to mix everything together. Cook for a few more minutes.

Add the tomato paste and stir well.

Add the fresh tomatoes (or tomato pulp) and mix well.

Slowly pour in the clear stock or chicken stock, stirring constantly to avoid lumps.

Add the bouquet garni and bring to a boil.

Lower the heat and simmer the sauce for 1.5 hours with the lid on the pan.

Remove the bouquet garni, taste the sauce and season with salt and pepper.