Over in the province we'd call that mince and onions, obviously being part of the island of Ireland the potatoes are inferred from kt being a meal.
The yanks might be taking the piss, but as far as I'm aware they put it in a bap and call it a sloppy Joe (which frankly sounds like a sex act).
Tangentially, other fine Northern Irish cuisine includes the vegetable roll, which is primarily a sliced beef sausage with a wee bit of onion and celery. Tasty.
Brother, just because you call your hamburger meat mince doesn't mean you know how to handle it better than us here in burgerland. Our sauce for it not only includes onions but also tomatoes and, in true American fashion, sugar(either from ketchup or brown sugar). And of course, said hamburger meat goes in a bun, not on a plate unless you're serving it with noodles from hamburger helper. What savages.
Looks like shepherd's/cottage pie to me, only someone couldn't be arsed to mash the potatoes and put the whole load in another dish and in to the oven for another hour, so just served it as is.
As long as there's some butter on those tatties, I personally don't see an issue. ¯\(ツ)/¯