Bring a medium saucepan of lightly salted water to the boil. Peel the potato and cut into 2cm chunks. Finely chop the chives and brown onion. Finely chop the garlic. Grate the celery and carrot.

Cook the potato in the boiling water until easily pierced with a knife, 10-15 minutes. Drain and return to the saucepan. Add the butter, milk and the salt and mash with a potato masher or fork until smooth. Stir through the grated Parmesan cheese and chives until well combined. Cover to keep warm.

While the potato is cooking, heat a drizzle of olive oil in a large frying pan over a high heat. Add the onion, celery, carrot and a generous pinch of salt and cook, stirring, until softened, 4-5 minutes. Transfer to a bowl. Return the pan to a high heat. Add the beef mince, garlic and another drizzle of olive oil to the pan. Cook, breaking up with a spoon, until just browned, 2-3 minutes. TIP: Transferring the veggies out of the pan allows the beef to brown!

Add the tomato paste, water and beef stock pot to the frying pan. Return the veggies to the pan. Stir to combine the beef and veggies. Add the baby spinach leaves and stir through until just wilted, 1 minute. Add a dash of water and stir through.

Preheat the grill to medium-high. Transfer the mince mixture to a baking dish and spread the mash on top. Grill until lightly golden, 5-7 minutes. TIP: Keep an eye on the mash topping as it can burn quickly!

Divide the beef and spinach cottage pie between bowls.