In a large pot, boil the potatoes until soft.

In a large saucepan, heat the oil on low.

Add the onion, mushrooms, salt, snd pepper, and cook until translucent.

Add the meat, incorporate, and cook through. NOTE: I used beef but, obviously, ground lamb could also be used, if you can find it at the supermarket. I couldn't when I put this together, but I still called it Shepherd's Pie because, like with Minced Meat Pies no longer having meat in them these days, just about everyone I know makes Shepherd's Pie with beef, so I figured no harm, no foul. If you are pedantic, I could have called this Cottage Pie, but, in the US, I don't think anyone knows what it is. Besides, I figured, who would want to be that guy, right?

Stir in the steak sauce, and let cool.

When cooled, stir in the eggs, and pour the mixture into the bottom of the large casserole. The eggs will firm up the bottom to provide a solid base.

Add the butter, oil, and carrots into the now-empty large saucepan, and simmer on medium until tender.

Add the corn niblets, peas, and salt, and mix and simmer until it's all happy and tender.

Layer the veggies on the meat in the casserole.

Drain, return to the pot, and mash the potatoes on low.

Add butter and salt while mashing. I know, it's a lot of butter, so cut it down to 2/3 stick if you like.

Add the milk to the potatoes. It will be loose at first, but it will firm up a bit while you stir it in a few minutes.

When the potatoes are stackably firm, scoop it on top of the casserole.

Throw it all in the oven at 375°F for 45 minutes.

OK, it will have this beautiful crust after 45min, and you are just going to sprinkle the cheddar over the top.

Broil for about 5 min, keeping an eye on it after 3 minutes to be sure it doesn't burn, to melt the cheese.

Remove from heat and try to let it cool about a half hour before diving in. As can be seen from my pic, I always fail. Enjoy.