Sausage & spring mash pie

Ingredients

• Milk – 100 ml.
• Potato – 1 1/2 kg (It should be cut into big chunks).
• Savoy cabbage – 1/ 4 to 1 /2 kg (It should be shredded).
• Butter – 50 grams.
• Vegetable oil – 2 teaspoons.
• Shallot – 10 nos. (They should be halved).
• Pork sausage – 10 nos.
• Dijon or wholegrain mustard – 1 tablespoon.
• Thickly sliced carrot – 4 nos.
• Mushroom – 2 packs of 250 gram each. (It should be quartered or halved).
• Thyme sprigs – 2 to 3 nos. (You can keep extra to serve).
• Beef stock – 300 ml.
• Caramelized red onion – 2 tablespoons.
• Full-bodied red wine – 400 ml.