Personally I would just mix a half pound of honey with the same volume of water.
Then add half of that gently stirring in. Once you're confident its fully incorporated, take a gravity test and a small taste.
Repeat as necessary. Taste is a better guide than a hydrometer at this stage, yet if you get your 1.010 target and the taste is "it might need a tiny bit more" then I'd leave it there as you may get some extra perception of sweetness recovering later.
Your main caveat is that sweetening with honey can sometimes cause a haze, which I believe is proteins. Be prepared for that.
If it did haze on you, its either further time to allow it to drop out or 2 part finings works for me -but I do usually fine it and then leave it for a month so any sediment can compact down before racking off to a bottling bucket.
Finally, your mead should have been stabilised with sulphite and sorbate prior to back sweetening.....