I was horrified that my friend makes hers in the blender.
And even more horrified that my MIL doesn't make them and buys multiple packets of M&S ready made mash.
I heat up a good glug of milk and a couple of tablespoon of butter in a pan , stir in some nutmeg and black pepper , add the potatoes, then use a hefty metal masher and mash the hell out of it. I find it fun.
Why would anyone blend mash?