Combine apple peels and cores with water in a saucepan.
Bring to a boil, then reduce heat and simmer for 30-45 minutes until peels and cores are very soft.
Strain the mixture through a fine-mesh strainer, pressing on the solids to extract as much liquid as possible.
Return the strained liquid to the saucepan and simmer until reduced by half, about 15-20 minutes, to create a syrup.
Add the syrup to your favorite applesauce recipe or use it to sweeten the
applesauce.
