In a good old fashioned notebook!
I have 3, one for purely recipes, one for technique & information about ingredients, and one for writing menus & jobs that need doing in the kitchen.
I have never made lists before in my life, and all notes I used to write on scrap paper (the back of tickets mainly) & store in a shoebox if they made it through the washing machine... but after my head chef left 2 months ago I had to massively step up my game to keep the place running (I've only been sous for 6 months, & only a chef for 2 years, no sign of a new head chef yet, plus 2AA rosettes to try and keep... wish me luck).
Lists and notebooks are the way for me, they don't break, run out of battery or wipe themselves of all content. I can't trust ipads or laptops not to do that, and I cannot risk losing these notes or I'd be massively in the poop.
I have a diary too, in which I write upcoming events/lunch parties. (Plus the SFBB book for the cleaning schedule).
Lots of books, but I don't have a good track record with laptops, when they get slow I shake them and then they cry and refuse to play with me anymore.
I'm looking into using computers (besides excel for the gp & invoice records), but after once losing essay work for a degree less than a week before due date I will never trust them again for important things. (Don't say ext hardrive because they break too sometimes.....Luckily for me I hand wrote the whole essay before typing it up, I just had to re-trace my notes & start over).
I never want that hideous sinking feeling again from computers, so all my important stuff is always handwritten, or typed into the quick 'notes' app on my phone & copied to paper later.