Is there some kind of priority to boss fate effects? Top to bottom? Sorry to ask another rules question but I couldn't find it
For the recipes start at the bottom and work your way up. Just remove any dice used in a previous recipe before checking the one above it. That's the official response, if I can find the link I'll edit.
Edit: From the unofficial FaQ
G.10 - If when rolling Fate Dice you have the correct symbols to potentially complete different recipes, how do you decide which to complete?
When checking Fate Dice results against recipes on a monster's card, you should start at the bottom of the card and work up. i.e. start at the bottom most recipe and work upwards, removing dice from the pool for any recipes you have completed.