Bring a medium saucepan of salted water to the boil. Peel potato and cut into large chunks (save time and get more fibre by leaving the potato unpeeled!). Finely chop onion and garlic. Grate celery and carrot. Roughly chop mixed leaves. Little cooks: Don your goggles and have a go at peeling off the onion's outer layer!

Cook potato in the boiling water until easily pierced with a fork, 12-15 minutes. Drain and return to pan. Add the butter, milk and the salt. Mash until smooth. Stir through grated Parmesan cheese until well combined. Cover to keep warm. Little cooks: Get those muscles working and help mash the potatoes!

In a large frying pan, heat a drizzle of olive oil over high heat. Cook onion, celery and carrot with a generous pinch of salt, stirring, until softened, 4-5 minutes. Transfer to a bowl. Return pan to high heat with another drizzle of olive oil. When oil is hot, cook beef mince and garlic, breaking up with a spoon, until just browned, 2-3 minutes. TIP: For best results, drain the oil from the pan at the end of this step.

Add tomato paste, the water and vegetable stock pot, stirring to combine. Add mixed leaves and cook, stirring, until just wilted, 1 minute. Return veggies to pan.

Preheat grill to medium-high. Transfer the beef filling to a baking dish. Spread mash over the top. Grill until cheese is melted and golden, 5-10 minutes (grills cook fast, so keep an eye on the pie!). Little cooks: Add the finishing touch by spreading the mash on top.

Divide beef and spinach cottage pie between plates to serve.