Place the apples in a slow cooker.
6 1/2 pounds apples - peeled, cored, and sliced 1-inch thick
In a medium bowl, combine sugars, cinnamon, nutmeg, cloves, allspice and salt.
1 cup granulated sugar, 1 cup dark brown sugar, packed , 1 tbsp ground cinnamon, 1/2 tsp freshly grated nutmeg, 1/4 tsp ground cloves, 1/4 tsp ground allspice, 1/4 tsp kosher salt
Pour the mixture over the apples and mix well.
Cover and place a long sheet of paper towels under the lid to catch condensation. Cook on low for about 10 hours (up to overnight), stirring occasionally, until the mixture is dark brown and starting to thicken.
Use an immersion blender to puree the apple butter until smooth. Continue to cook uncovered on low for about 2 hours, to remove most of the moisture. (you want a dark brown, thick mixture)
Turn off the slow cooker, then stir in vanilla. Let it cool, then transfer it to jars or airtight containers.
1 tbsp pure vanilla extract
Serve on slices of bread, muffins, pork chops or just eat it with a spoon.