Preheat the oven to 400°F. Lightly coat a 9-by-13-inch baking dish with nonstick cooking spray.

Heat the olive oil in a large skillet over medium-high heat. Add the onion and cook for about 5 minutes, stirring occasionally, until translucent.

Reduce the heat to medium. Add the ground lamb and cook for about 5–7 minutes, breaking it into crumbles and stirring occasionally until browned. Drain any excess grease.

Pour the red wine into the skillet, scraping up any browned bits from the bottom of the pan. Simmer for 2–3 minutes, until the liquid has reduced by about half.

Add the carrots, garlic, tomato paste, Worcestershire sauce, rosemary, thyme, peas, corn, half the parsley, salt, and pepper. Stir well to combine. Reduce the heat to low and cook for another 3–4 minutes, stirring occasionally.

In a small bowl, whisk the flour and cold beef broth together until smooth. Pour the mixture into the skillet, stirring constantly. Continue cooking for 2–3 minutes, until the filling thickens into a rich gravy.

Transfer the lamb mixture to the prepared baking dish. Spoon the mashed potatoes evenly over the filling, spreading gently to cover the entire surface. Sprinkle the shredded cheddar cheese over the potatoes.

Bake uncovered for approximately 30 minutes, until the filling is bubbling and the potatoes are lightly golden brown. For a more golden topping, broil briefly at the end, watching carefully to prevent burning.

Remove from the oven and let stand for 5 minutes before serving. Garnish with the remaining fresh parsley.

Serve and enjoy!