Peel and cut the potatoes, sweet potatoes and celeriac into large chunks. Cut the regular potatoes a little smaller than the other two items. Add them to a large pot of boiling salted water.

Gently boil them for about 25-30 minutes or until a fork goes into them easily.

Drain them and then add them back to the pot to mash with a potato masher or use electric beaters. Add the butter, milk and a good pinch of salt and pepper and mash. Add more milk if it is too dry. Set aside the mashed potatoes, sweet potatoes and celeriac for later.

In a large frying pan with a lid, brown the ground beef over a medium heat. When it is browned, drain the excess fat and add the onions, garlic and carrots with a good pinch of salt and pepper.

Stir and let carrots and onions soften for several minutes.

Preheat the oven to 400 degrees F.

Add the flour and stir it into the meat mixture then add the Worcestershire Sauce, tomato paste (or ketchup) and beef stock. Stir and reduce the heat to low. Cover the pan and let the meat simmer gently for 15 minutes. If it seems too thick then add a couple more tablespoons of beef broth. The sauce should not be runny at all. If it is, take the lid off and let the excess liquid evaporate. Check to see if you need any salt or pepper and add it if necessary.

Add the frozen peas and corn and stir to distribute the vegetables evenly.

Divide the beef mixture into the two dishes (see notes) and spread it out evenly.

Drop dollops of the mash onto several spots on the meat and then spread it out to cover the beef. Use 2/3 on the large dish and 1/3 on the smaller dish. If you like, you can drag a fork over the surface of the mash to make little lines for texture.

Cover and freeze the smaller dish for another day.

Bake the larger dish at 400 degrees F for 25-30 minutes or until it is bubbling at the edges.

Let it sit for a few minutes when you take it out of the oven. Serve with HP Sauce, ketchup or as it is.