• See Notes for making ahead. Firstly, start with making the cheesy mashed potato topping - put the potatoes in a medium saucepan of cold water, bring to the boil and add some cooking salt.   Cook on a continuous simmer for 15 to 18 minutes, until the potatoes are tender.
• Meanwhile, brown the mince with 1 tbsp of olive oil over a high heat in a large saucepan or casserole, breaking it up with a wooden spoon. Once browned (this will take around 5 minutes), remove from the pan into a bowl and set aside.
• Add the other tbsp of olive oil to the pan along with the onion, carrots and celery. Reduce the heat to medium low and cook for 20 minutes, until the vegetables are soft, stirring occasionally.
• When the potatoes are cooked, drain well in a colander and let them sit for a minute or 2 to steam dry.   Meanwhile, add the milk and butter to the saucepan and put on a low heat to warm the milk and melt the butter.   Turn off the heat and add the cooked potatoes.   Mash well until the potatoes are smooth and the milk and butter are combined.   Season with salt, if needed, and black pepper, to taste and stir in the 65g of grated cheese. Set aside until needed at step 2 below.
• Once the vegetables are soft,  add the garlic, flour and tomoto puree, increase the heat to medium and cook for 2 minutes, stirring constantly. Now add the browned mince to the pan and pour in the wine, stir to combine, increase the heat to high and reduce slightly (about 2 to 3 minutes).
• Stir in the stock, Worcestershire sauce, thyme and bay leaf. Bring to a simmer and cook for 45 minutes, uncovered.  Heat the oven to 180C/160C fan/gas 4.
• Remove the thyme sprigs, if using, and bay leaf, stir in the peas and season with salt and freshly ground black pepper, to taste.

Assemble and bake the pie:

• Transfer the mince to a suitable pie dish or ovenproof dish (I use a 26cm round pie dish or 27cm x 20cm rectangular dish). Leave to cool slightly for 15 minutes.
• Top the mince with the mash, using a fork to make a decorative pattern. Scatter over the 25g grated cheese.
• Bake the pie in the oven for 40 minutes, turning the dish around halfway through, until the potato topping is lightly golden and the filling is piping hot.   Serve with green veg of your choice.