Preheat oven to 350F.
Line a mini muffin pan with baking liners.
Mix together oats, milk, apple butter, and eggs.
Whisk together flour, ½ cup sugar, baking powder, baking soda, and salt.
Add wet ingredients to dry ingredients and mix until just combined.
Stir in raisins, if using, and grated apple.
Spoon the batter into the prepared pan – about 1 Tablespoon per mini muffin.
Bake until golden and a toothpick inserted in the center comes out dry, 8-12 minutes.
Transfer to a rack to cool completely.