Beef bourguignon with celeriac mash

Name: Beef bourguignon with celeriac mash
Ingredients: 1 tbsp goose fat; 600g shin beef, cut into large chunks; 100g smoked streaky bacon, sliced; 350g shallot or pearl onions, peeled; 250g chestnut mushrooms (about 20); 2 garlic cloves, sliced; 1 bouquet garni (see know-how below); 1 tbsp tomato purée; 750ml bottle red wine, Burgundy is good; 600g (about 1) celeriac; 2 tbsp olive oil, plus a glug; 1 or 2 rosemary and thyme sprigs; 2 bay leaves; 4 cardamom pods