Whisk together cornstarch and apple juice. Set aside. Bring butter, pears, ginger and salt to a boil. Reduce heat to low-medium and continue cooking, stirring occasionally, until pears begin to soften, about 6-8 minutes. Do not overcook. Remove softened pears from heat and stir in cornstarch mixture. Return to heat and cook until thickened, about 1 minute.
Cool completely before using.