Crockpot Apple Butter

10 pounds apples - peeled, cored and sliced
3 cups granulated sugar, brown sugar, lightly packed, or a mixture
1 1/2 Tab. ground cinnamon
3/4 teaspoon grated nutmeg
1/4 teaspoon ground cloves
1/2 teaspoon salt
1 1/2 Tablespoon vanilla

Place the apples in a slow cooker. Add sugar, cinnamon, nutmeg, cloves and salt.
Cook in slow cooker on low for about 10 hours, stirring occasionally, until the mixture is thickened and dark brown.
Uncover, stir in vanilla and continue cooking uncovered on low for about 2 hours.
Use an immersion blender to puree the apple butter until smooth.
Spoon the mixture into containers, cover and refrigerate for up to two weeks or freeze.