Put the bread, pancetta, shallots and herbs in a food processor or mini chopper and blitz until finely ground.
Place in a bowl with the mince, egg, mustard and salt and mix together thoroughly with your hands. Cover and put in the fridge for an hour or overnight.
With wet hands, roll about a tablespoon of mince for each meatball until you have used up all the mix.
Heat a little vegetable oil in a large frying pan and fry the meatballs, in batches, until nicely browned all over. Place in an ovenproof dish and set aside.
Put the ale, shallots, garlic and rosemary in a medium pot and bring to the boil. Reduce heat to a simmer and cook until the liquid is reduced by about half.
Add the chicken stock, cornflour and sugar and bring to the boil again. Reduce the heat once more and simmer for 20 minutes.
Preheat the oven to 190C (380F). Strain the gravy over the meatballs and bake for 15-20 minutes or until the gravy is bubbling and thickened.
Sprinkle with the chopped herbs and serve with potato or celeriac mash and wilted spinach.