Is there a recipe that utilizes mashed potatoes rather then puff pastry for meatloaf Wellington

Good to know, thanks.

Look for a 'frosted' meatloaf recipe. The frosting in this case is mashed potatoes....

I would argue that the duxelles or pâté plus the puff pastry is what makes it Wellington. If you subbed out mashed potatoes (I guess by piling them around the beef?) really you’d have what, a wicked fancy sort of shepherds pie? If you’re looking for tenderloin and potatoes I’d make just that and forget about Wellington.

Haven't seen one.
But there are plenty of recipes for beef pot pie with either mashed potato or crisp potato crust.
Have a look at them and see if one looks good to you.