Festive chestnut & seed roast with vegan mushroom gravy

onion 25.0% , Mushroom Gravy Sachet 25.0% , fortified wheat flour 16.5% , seed 8.0% , mushroom 4.2% , onion 4.1% , spinach 4.0% , chestnut 3.5% , lentils 3.0% , rapeseed oil 2.6% , water 2.1% , leek 1.1% , red onion 0.5% , garlic 0.3% , wheat gluten 0.1% , rye flour 0.1% , cranberry 0.0% , yeast extract 0.0% , apple juice from concentrate 0.0% , pea fiber 0.0% , salt 0.0% , maltodextrin 0.0% , mushroom 0.0% , demerara sugar 0.0% , lemon juice from concentrate 0.0% , thyme 0.0% , sugar 0.0% , onion 0.0% , garlic 0.0% , Onion Extract 0.0% , turmeric 0.0% , white pepper 0.0% , sage 0.0% , parsley 0.0% , yeast 0.0% , tomato 0.0% , Acidity regulator 0.0% , rosemary 0.0% , sunflower oil 0.0% , black pepper 0.0% , allspice 0.0% , coriander 0.0% , ginger 0.0% , Stabiliser 0.0% , marjoram 0.0% , flavouring 0.0% , Preservative 0.0% , E160c 0.0%