Lots and lots of butter. And then, add more butter just in case. I entomb mine in streaky bacon & bought a meat syringe I inject more butter into the bird with. I melt the butter with sage & pepper for a bit of flavour.
Double wrap the foil, baste often, use a meat thermometer to make sure it’s reached temperature & hasn’t over cooked.
I also slide my fingers under the.skin & add lots of sausagemeat, along the top of the breast & in the dip by its bottom. Well, I think it’s it’s bottom. The opposite end of the cavity lol!
Celery, a small onion & a carrot (and butter!) in the cavity.
Most importantly, once you’ve prepped al of that, re-weigh the bird - I can easily add a 1.5kg of bacon, sausagemeat etc. - and calculate the cooking time based on that.
Saying all this, it’s only my husband & I for Christmas dinner (and one to drop at Mum’s!) this year, so I’m deconstructing a turkey breast joint to add the above!