Venison braised in verjuice with chestnuts and pine mushrooms

Ingredients

• 1 kg deboned venison shoulder, cut into 4cm pieces
• 55 g (¼ cup) plain flour
• salt and pepper, to season
• 80 ml (⅓ cup) olive oil
• 1 onion, finely chopped
• 1 carrot, peeled, finely chopped
• 2 celery stalks, finely chopped
• 1 handful of picked woody herb leaves (such as rosemary, thyme and bay leaves)
• 375 ml (1½ cups) verjuice (see Note)
• 250 ml (1 cup) veal stock
• 3 cups thinly sliced pine or brown mushrooms
• 10-12 chestnuts, baked, peeled
• creamy potato mash, to serve