Heat the oil in a large heavy base saucepan. Add the onion, celery, carrot and zucchini and cook for 5mins until it begins to sweat and soften. Add in garlic cloves and cook off for 1min. Add in the mince and cook in 2-3mins until it starts to brown.

Stir in tomato paste, beef stock, diced tomatoes and wosterchire sauce. Combine corn flour with 1tbsp of water in a small bowl to remove lumps and then stir it into your mince mixture. Bring the mixture to a bowl and then reduce to a simmer and cook for a further 10-15min until it starts to thicken. Stir occasionally to prevent it sticking. Allow to cool slightly while you make the mash.

Preheat the oven to 200C.

Add potatoes to a large saucepan and top with water. Heat on high until water begins to boil. Cook for 7-10mins until potatoes are soft. Drain the potatoes and then add back into the saucepan. Use a potato masher or fork to mash the potatoes whisk in butter and milk into the potatoes until they are smooth.

Pour mince into a large baking dish and then spread mashed potato over the mince. Use a fork to drag it along the potato, this will create a crunchy top! Sprinkle with parmesan and then bake in the oven for 40-50min until meat is bumbling and potato is crunchy and golden.