It's actually best to leave it until spring. The old growth will help protect the crown.
I'd leave it til spring. Top growth does offer a bit of protection to the base.
All of my hardy fuschias have been frosted now. They're at the stage of having dying leaves still hanging on. I know it infuriates me them looking like that, but after the next frost a stiff wind will blow them all off.
In the spring you'll notice regrowth lower down on the stems. That's where you cut back. If you've do it too early the new growth can also get frosted. Yes mulch around the plant now whilst the soil is still moist to protect the roots. J.
H/JF the hardy varieties often do have smaller flowers IME. Oh apart from Mrs Popple that is- I assume my Dads' plant is that. Just know it withstands very cold winters in WMidlands & has done many yrs. I've got a couple now in my garden & yet more cuttings, just in case. Just call it Dad's fuschia!
I grow Greyrigg & Hawkeshead. GR definitely is hardy, came trough the last couple of winters up here. Late at restarting in spring, but very delicate white/pale pink flowers. There's a good sized shrub of it at Harlow Carr which I spotted last yr.
Hawkeshead, which has small white flowers, I did actually lose- when I didnt protect its' roots in a large pot! So I now have a new plant in the ground & several good cuttings- still in my porch! J.
Fuchsia, after Leonhart Fuchs (German botanist).