Has anyone done the milk ladder with their baby?

[GoodVibesOnlyPlease]

We're just about to start week 5 of the milk ladder to get our almost one year old to be able to have lactose again after an illness caused temporary intolerance.
Week 5 is boiling milk for a couple of minutes and then allowing to cool to room temperature, has anyone else done this and know if you can then put the milk back in the fridge to make it last the day?Or mix with breast milk? Or does this defeat the whole purpose of boiling the milk?

We're doing a milk ladder at the moment (ours is a bit different but the principles will probably be similar). For the baked/cooked/boiled steps, we've been fine keeping things in the fridge - DC isn't a huge fan of cold cows milk though (or any cows milk actually, most of it gets firmly rejected) so we do need to warm things through for them to drink it. We've also done mixing with breast milk and that's been fine - when babies are on formula it's considered ok to mix formulas at the relevant steps, so our dietitian said it's fine to do the same with breast milk if they'll tolerate it.

Oh fab, thank you! We're not under a dietitian, just been told to Google it and get on with it by the GP 🙄 luckily it's working and he's back to being able to tolerate everything we've done so far.