In a large saucepan heat 1-2 tbsp oil over medium heat and gently fry the onion for 8’ – 10’ until golden but not burned. Add the tomato purée and continue frying for a few more minutes until it has released its fragrance too. Raise the heat and add the mince, frying and turning regularly until brown.
Add the wine, if using, and let it simmer for 5’ until most of the alcohol evaporates. Now add the carrots, stir them through and pour the stock and the Worcestershire sauce, season with salt and pepper and give it a good gentle stir, lower the heat and cook gently and uncovered until the carrots are soft, about 30’, and the stock has reduced. By this time the stock should be thick. If not, dust with the flour, mix well to dissolve it and slowly simmer for another 5’-10’. Throw in the peas, at the last minute, give the mix a good gentle stir and let it simmer for 5’ more before removing from heat.
Now it’s time to crack on with the mash. In a deep pot, cover the potatoes (and parsnips if using) in cold water and bring to the boil. Lower the temperature and simmer until tender for approx 20’. Meanwhile preheat the oven to 180 C. When the vegetables are done, drain the water and in the same pot mash thoroughly with a potato masher or a fork. Make sure you mash everything well to avoid lumpy bits- be patient my friends! Start adding milk (or cream), one dash at a time and a knob of butter, the mustard and a generous pinch of nutmeg and mix with a spoon. The mash must be velvety and fluffy; not too stodgy and not runny. Taste and season with salt and pepper.
Take an ovenproof dish (mine is 18cm x27cm) and pour the mince, spreading it evenly. With a spoon or spatula take big dollops of mash and spread it over the mince to cover it completely. Don’t throw or pour the mash in the mince! For that “wow” factor, take a fork and gently draw wavy lines, vertically or horizontally, from one side of the dish to the other. Continue you’ve made a wavy pattern all over the mash. Finally sprinkle the cheese. Stick in the oven, on the middle shelf and bake for 30’-40’ until the cheese has melted and the top gets golden and crusty. You can use the grill at the very end if you need an extra crunch on your mash. Remove from the oven and wait 10’ before you serve. Voila!