2) Place the single cream and butter into a microwave-safe container and heat in the microwave until warmed through, about 35 seconds. Drain the potatoes in a colander and then return to the saucepan. Mash the potatoes and then add the single cream and butter, salt and pepper; continue to mash until smooth. Stir in the egg yolk until well combined.
3) Preheat the oven to 200C/Gas 6. Place the rapeseed oil into a 30cm frying pan and set over a medium high heat. Once the oil shimmers, add the onion and carrots and saute just until they begin to take on colour, approximately 3 to 4 minutes. Add the garlic and stir to combine.
4) Add the lamb, salt and pepper and cook until browned and cooked through, approximately 3 minutes. Sprinkle the meat with the flour and toss to coat, continuing to cook for another minute. Add the tomato purée, chicken stock, Worcestershire sauce, rosemary and thyme, and stir to combine. Bring to the boil, reduce the heat to low, cover and simmer slowly for 10 to 12 minutes or until the sauce is thickened slightly.
5) Add the corn and peas to the lamb mixture and then spread it evenly into an 28cm by 18cm glass baking dish. Top with the mashed potatoes, starting around the edges to create a seal to prevent the mixture from bubbling up. Smooth the top with a rubber spatula. Place on a greaseproof paper lined tray on the middle shelf of the oven and bake for 25 minutes or just until the potatoes begin to brown. Remove to a cooling rack for at least 15 minutes before serving.