It appears that cottage pies are made with beef and shepherd's pies are made with lamb
This recipe has quite a few steps, and requires quite a bit of work, and it may get a little hectic if you're making other dishes, but it tastes great!
I made this for a half Christmas, half end-of-the-world-eve dinner party at my place, and apart from the slightly raw garlic in the mashed potatoes, everyone loved it!