Add Sorbistat K along with some Potassium Metabisulfite (The Sorbistat will tell you how much Kmeta to use). Then backsweeten with more juice or sugar and force carb. I do this with my apfelwine, backsweetening with a gallon of juice.
Sorbistat K is Potassium Sorbate and will prevent fermentation. It will NOT stop an active fermentation to let the cider ferment completely first.
EDIT: Found my notes; use 20ml of a 10% Kmeta solution anlong with 4g or Sorbistat K. This is for 5 gallons. Sweeten to taste.
Something is always fermenting....
"It's Bahl Hornin'"
Kegged: Sour Saison, Pale Ale, Aggie Ale, Firestone DBA, De Koninck Blonde
Bottled: Belgian Quad (Grand Reserve), Derangement (Belgian Dark Strong)
On Deck: Pliny the Younger