Cook the beans over gentle heat for 45 minutes or an hour at the most (an hour-and-a-half if they are dried, after soaking in water, together with the herbs and garlic, for a couple of hours). In either case, do not add salt which tends to harden the skins.
Puree by putting through a vegetable mill, carefully eliminating the husks.
Put the garlic, rosemary, sage and cubed bacon to saute briefly in a saucepan with 4 tablespoons of oil.
Pour on the bean puree. Season lightly with salt and the red hot pepper to taste. Stir to blend the flavours and bring slowly to the boil.
Throw the pasta into the puree and cook until firm, diluting with a little of the bean cooking water, but only if necessary - the soup must be thick and rather solid.
It is excellent hot, but is absolutely delicious if heated up with the addition of a drop of first-rate olive oil.
If you prefer, leave a few beans whole and add them to the saucepan with the puree. Some cooks hold that a carrot is not out of place in the mirepoix (but then cut out the bacon), or that the soup loses nothing if you add a little tomato, even tomato concentrate (paste).