Bit of both. Generally what happens is that I come across a reference to a dish that makes me want to try it, then look up a bunch of recipes to get an understanding of how to make it, mix and match from the recipes I’ve found, then write up what I did. But I could probably buy the ingredients and cook at least half of these dishes from memory.

I also maintain a spreadsheet of what I cook every day which helps me not repeat dishes too often (e.g. I can tell you that it’s only been 21 days since I last cooked the Za’tar Salmon and Spinach Rice someone else asked about in another comment, so I’ll probably give it at least a month before I cook it again.

I also score (and get the wife and kids to score) each meal when I first cook it (to my satisfaction - sometimes it takes a couple of goes to tweak it). The ones I listed here are all ones which worked out ok and which I enjoyed. The kids inevitably score veg-based meals low but I mostly ignore them!