Help me make Shepherd's Pie.
Here's a recipe for Shepherd's Pie:

Ingredients:

• 2 tablespoons olive oil
• 3 lb ground lamb
• salt, to taste
• pepper, to taste
• 1 large onion, chopped
• 3 large carrots
• 6 cloves garlic, grated
• 1 tablespoon fresh thyme, chopped
• 1 tablespoon fresh rosemary, chopped
• 2 tablespoons tomato paste
• 2 tablespoons worcestershire sauce
• 1 cup red wine
• 1 cup chicken stock
• 3 lb yukon gold potato, cubed
• 1/4 cup unsalted butter, 1/2 stick
• 4 large egg yolks
• 1 cup sour cream
• 1 cup grated parmesan cheese

Instructions:

1. Preheat the oven to 425°F (220˚C).
2. Heat the oil in a large pan over medium-high heat until shimmering. Add the ground lamb, season with salt and pepper, and fry for 5 minutes, until cooked through.
3. Add the onion, carrots, garlic, thyme, and rosemary, stir, and cook for about 10 minutes, or until the veggies are softened and the meat is well-browned.
4. Add the tomato paste and Worcestershire sauce and stir to incorporate. Cook for 1-2 minutes, stirring constantly, until the liquid evaporates and the meat is aromatic.
5. Pour in the red wine and reduce until almost completely evaporated.
6. Add the chicken stock, bring to a boil, and cook the meat until the stock has evaporated, 5 minutes.
7. Meanwhile, cook the potatoes in a large pot of boiling salted water until tender. Drain, then return to the hot pan over low heat to dry out a bit.
8. Transfer the potatoes to a large bowl and mash until smooth.
9. Add salt, the butter, egg yolks, sour cream, and Parmesan cheese. Fold until well combined.
10. Transfer the potatoes to a piping bag or zip-top bag fitted with a star tip.
11. Spoon the lamb mixture into a large baking dish. Pipe the golden mashed potatoes over the lamb.
12. Bake for 30 minutes, until the potatoes are golden brown.

Enjoy your Shepherd's Pie!