If you don't have mash, chop up two potatoes (skins and all unless they're made of leather), pop them in cold water, bring them to the boil until a fork pierces them easily (about 20 mins), then drain and mash them with butter, salt, pepper, and a splash of milk. More detail here if you're unsure.
Quicketysticks summary: grease an oven bowl / casserole dish, put the bolognese in, the mash on top, cook at 180 degrees for 30-45 minutes, done. And in pictures...
Never have ingredients looked so humble. OR SO READY.
Heat the oven to 180 degrees with as much accuracy as your oven does or doesn't allow.
Grease the butter dish. I save butter wrappers for this - when the butter's finished, I tear the wrapper into two squares and put them in the fridge.
A thoroughly greased bowl.
My mash was a bit thick to spread on top, so I added a splash of milk to it. But I added too much, so...
I cracked an egg in to help bind it and thicken it again. Feel free to just add the right amount of milk to start with, instead.
That took about two minutes. Ready to go in the oven... and of course I didn't get a photo of when it was lovely and golden and delicious looking, I'm a bit rubbish at and-here's-the-finished-meal photos, but you'll recognise it when you make it. (It'll be the same dish you put in the oven, only hot and golden now.)