Follow these steps to create the perfect Cottage Pie:

1. Prepare the Mashed Potatoes: Start by boiling the potatoes in salted water until tender. Drain and mash with butter and milk. Season to taste and set aside.

2. Cook the Meat: In a large skillet, heat olive oil over medium heat. Add the diced onion, carrots, and celery. Sauté for about 5 minutes until softened.

3. Add the Ground Meat: Increase the heat and add the ground beef or lamb to the skillet. Cook until browned, breaking it up into small pieces.

4. Incorporate Flavor: Add the minced garlic, tomato paste, Worcestershire sauce, thyme, and rosemary. Stir well for 1-2 minutes until the ingredients are fragrant.

5. Simmer the Filling: Pour in the beef or vegetable broth, scraping the bottom of the skillet to deglaze. Bring to a simmer and let cook for about 10 minutes. Stir in frozen peas, season with salt and pepper, and remove from heat.

6. Assemble the Pie: Preheat your oven to 400°F (200°C). In a baking dish, layer the meat mixture on the bottom. Spread the mashed potatoes over the meat, smoothing it out evenly. If desired, sprinkle shredded cheese on top.

7. Bake: Place in the preheated oven and bake for 25-30 minutes, or until the top is golden brown and the filling is bubbling.

8. Rest and Serve: Let the Cottage Pie rest for about 10-15 minutes before serving. This helps the layers set and improves the dish’s texture.

These simple steps will lead you to a delicious Cottage Pie, full of hearty flavors that will impress everyone around your table.