Ye thought I was joking about this. I was not! Nuair a bhí mé i mo pháiste, d'ith mé mórán lumpy mash, and I hated it. As soon as I was old enough to cook, I swore never again would my mash be lumpy!
Step one: peel your spuds in warm water. https://twitter.com/Motherfocloir/status/1308651066033135616

I like to use a peeler because I feel I lose less of the potato with it. I'll gather up the peels for @geekgirlpsych's compost pile. Céim a dó: cut the spuds into roughly equal sized pieces.

Fiú na prátaí beag get a wee chop. I'm not a saineolaí potatoes, so I don't know why, but it helps.
I do know that Céim a trí: starch rinse is ríthábhachtach. Pour cold water on your spuds and give them a swirl. Pour off this cold water.

This is the water that pours off. If you like your spuds gloopy and manky, do not do this step. If you are a right and proper thinking person, step 3 is the key.

Bhris mé an sruth! I broke the thread! Here's céim 4: https://twitter.com/Motherfocloir/status/1308692578880098304?s=19

Céim 5: when your potatoes are boiling, set a timer for about 15 minutes. I had set mine for 15 minutes, but it took me a minute or two to get a photo of the clock on the cooker...

It's also a good idea to crack the lid on the pot so it doesn't boil over.

Optional céim 6: put on a load of washing or load the dishwasher.

Céim 6: when your timer goes, take a fork or a sharp knife, and prick the potatoes. They should be tender, not hard. I got my sizes a bit mixed, so a few of my bigger chunks aren't done yet. I've added 2 minutes to the timer. Don't leave it much longer, or you risk mush.

Céim 7: teem the potatoes! Pour off all the water. Then let the potatoes rest for about 5 minutes. My mam has always done a double layer of kitchen paper between the lid and the pot: it absorbs the steam to let the potatoes dry out a little, while not letting all the heat out.

Letting the spuds sit about 5 minutes is good. They're noticeably fluffier afterwards.

Céim 7: now, we mash!
A proper masher is crucial here. A few people have (rightly) pointed out that a ricer will give beautiful light mash. I love a ricer for Christmas mash.

For every day mash, you want s masher that is firm to the edges while giving good coverage. I have two main mashers at the minute. Lefty is my fave - solid coverage, stiff, but with a little flex. The one on the right is great for a rougher mash, or for doing other veg.

As you mash, make sure to get the edges. You want to give a nice mash, without letting the potatoes get cold. Here's where I'm stopping to add some butter.

I've added a healthy knob of butter and a splash of milk, and given them a wee mash through. If I weren't planning on feeding a chunk of this to a toddler, I'd also add salt and pepper at this stage.

Céim 8 (?): Críoch! Is é an rud is tábhachtaí ná remember not to eat them all before the rest of the family is there.

Thanks for indulging me in this! I know it's not exactly rocket surgery, but given the state of the world right now, I like to control the things I can, and one of those is the state of my mash. It is a personal favourite comfort food.