Prepare the Pork Filling: Heat olive oil in a large skillet over medium heat. Add onions, carrots, and celery and cook until softened, about 5 minutes. Stir in garlic and cook for an additional minute. Increase the heat to medium-high, add ground pork, and cook until browned, breaking it apart with a spoon. Mix in tomato paste and sauté for 2 more minutes. Pour in stock, Worcestershire sauce, thyme, salt, and pepper.
Simmer on low heat for 15-20 minutes or until thickened. Taste and adjust seasoning as needed.
Prepare the Mashed Potatoes: Place potatoes in a pot of boiling salted water and cook until fork-tender, about 15-20 minutes. Drain and return the potatoes to the pot. Add milk and butter, mashing until smooth. Season with salt and pepper. If desired, mix in Parmesan cheese for extra richness.
Assemble the Pie: Preheat your oven to 200°C (400°F). Transfer the pork filling to a baking dish. Spread the mashed potatoes evenly over the pork filling, using a fork to create peaks that will crisp up in the oven.
Bake in the oven for 20-25 minutes or until the potato topping is golden brown and crisp.
Serve: Allow the cottage pie to cool slightly, then serve it garnished with fresh parsley or another herb of your choice for a fresh touch.
