Level 18 - Valkyrie Spear
So, the recipe calls for 2 "good" items, which, when mastered can be used to autocraft via the Upgraded crafting slots - standard stuff.
The trouble I was having was that I had mastered 1 of these items (spear), and had the "good" version of the item I hadn't mastered (stiletto) in inventory. So, in actuality, I had everything I needed - the good version of the stiletto in inventory, and mastery of the spear.
The quirk is - if you don't have BOTH recipes mastered, it won't let you autocraft via the upgraded crafting slots, EVEN IF, you have the upgraded item in your inventory. It's either, have both in your inventory, or have both mastered.. Not, one in inventory and one mastered.
Not a huge deal, I went and mastered the stiletto for ease's sake - but I can see if this translates to higher level items that this quirk might be more impactful.