First, preheat your oven to 350°F.
In a large pan, heat the oil until it’s sizzling.
Season the ground lamb and fry it in the hot oil over moderate to high heat for 2-3 minutes.
Stir in the onions and carrot, and grate in the garlic.
Add Worcestershire sauce, tomato paste, and herbs, and cook for 1-2 minutes while stirring constantly.
Pour in the red wine and let it reduce until it’s almost gone.
Add the chicken stock, bring it to a boil, and let it simmer until the sauce thickens. Season with salt and pepper to your liking.
While the sauce is simmering, cook the potatoes in boiling salted water until they’re tender.
Drain the potatoes and briefly return them to the hot pan to dry out.
Use a potato ricer to mash the potatoes, then mix in the egg yolks, cream, and butter, followed by about 2 tbsp of grated Parmesan. Check for seasoning.
Spoon the lamb mixture into the bottom of an ovenproof dish.
Take a large spoon and generously layer the mashed potato on top of the lamb mixture, starting from the outside and working your way into the middle.
Sprinkle the remaining Parmesan on top and season it.
To create a rustic appearance, use a fork to fluff up the mashed potato, making rough peaks.
Bake in the oven for approximately 20 minutes, until it’s bubbling and golden brown.