Remove the shell from the chestnuts while they are still hot.
Heat a frying pan and cook the onions with the bacon and the garlic with some cooking fat over a medium heat until the onions are soft.
¼ lb bacon, 2 onions, 1 clove garlic, Cooking fat
Meanwhile, mash the roasted chestnuts in a bowl with a potato masher. Break them with a spoon of fork beforehand so they are easier to mash.
Add the mashed chestnuts to the cooked onions and bacon as well as 5 tablespoon cooking fat and the lemon juice and zest.
Zest and juice of 1 lemon, Sea salt and freshly ground black pepper to taste
Continue cooking over a medium-low heat until everything is well combined and warmed up.
You can now use the stuffing right away in the cavity of a chicken or turkey for roasting or you can bake the stuffing separately for about 45 minutes in a 375 F oven, until nice and brown on top.