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

Add the potato to the boiling water and cook until easily pierced with a knife, 10-15 minutes. Drain and return to the saucepan. Add the butter, milk and the salt, then 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 the veggies to a bowl. Return the pan to a high heat with a drizzle of olive oil. Cook the beef mince and garlic, 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 and water to the frying pan and crumble in the beef stock (1 cube for 2 people / 2 cubes for 4 people). Stir to combine. Return the veggies to the pan and stir to combine. 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: Grills cook fast, so keep an eye on the pie!

Divide the beef and spinach cottage pie between bowls.