Heat a Dutch oven over medium-high heat and add beef tallow. Season short ribs with salt and sear on both sides until golden. Remove and set aside.
Remove sausage from casings, brown in the pot, then remove.
Blitz onion, carrot, celery, garlic and thyme in a food processor to a fine dice. Add to the pot and cook until moisture evaporates and the mix begins to sizzle.
Deglaze with red wine and reduce by half.
Add tomato puree, beef stock and 500ml water. Return ribs and sausage to the pot. Bring to a simmer and cook gently for 1.5–3 hours until the ribs fall apart.
Shred the ribs, discard bones and return meat to the sauce. Season to taste.
Layer lasagne with pasta sheets, béchamel, ragu and mozzarella.
Bake at 180°C for 30 minutes covered with foil, then grill uncovered for 10 minutes to brown the top.
Rest for 10–15 minutes before serving.
