Preheat the oven to 180°C (350°F).

Heat the olive oil in a large skillet over medium heat. Add the chopped onion, diced carrots, and minced garlic. Sauté until the vegetables are softened, about 5 minutes.

Add the ground beef to the skillet and cook until browned, breaking it up with a wooden spoon.

Stir in the tomato paste, beef stock, Worcestershire sauce, dried thyme, dried rosemary, salt, and pepper. Bring the mixture to a simmer and let it cook for about 10 minutes, allowing the flavours to meld together. Remove from heat.

Meanwhile, place the potato chunks in a large pot of salted water. Bring to a boil and cook until the potatoes are tender when pierced with a fork, approximately 15-20 minutes. Drain the potatoes and return them to the pot.

Add the milk and butter to the pot with the potatoes. Mash the potatoes until smooth and creamy. Season with salt and pepper to taste.

Transfer the beef mixture to a baking dish and spread the mashed potatoes evenly over the top. If desired, sprinkle grated cheese on top of the mashed potatoes.

Place the baking dish in the preheated oven and bake for 30-35 minutes, or until the top is golden and the filling is bubbling.

Remove from the oven and let it cool for a few minutes before serving.

Serve the cottage pie hot and enjoy!