Pour the water into the slow cooker. Trim the top and bottom off each pear, peel it, halve it, and remove the core. Roughly chop the pears and add them to the slow cooker.

Add the cinnamon, nutmeg, cloves, and vanilla to the pears. Stir to combine and add optional sugar if desired.

Cover and cook on low for 3 to 4 hours or on high for about 2 hours until the pears are very soft and fall apart when stirred.

Blend the cooked pears until smooth using an immersion blender or carefully blend in batches. If the sauce is too thick, add water 2 tablespoons at a time until the desired consistency is reached.

For stovetop method, use a heavy-bottomed saucepan, cook uncovered over low heat for 1 to 2 hours, then blend and cool.