Preheat oven to 375°F/190 C. Grease a ½ cup/120ml muffin tin (or line with paper liners).
Chop the apple into ½ inch chunks. Feel free to leave the outer peel of the apple for some extra fiber.
Prepare the batter. In a large bowl, combine the brown sugar alternative, avocado oil, and apple sauce. Whisk until well combined.
Whisk in the almond milk and vanilla.
Add in the flour, baking powder, salt, and spices. Fold in until just mixed, does not have not have to be completely smooth.
Fold in most of the apple chunks (optional: reserve a few to place on top) until just combined. Set aside.
Make the crumb topping. In a small bowl, combine all ingredients except water and avocado oil. Stir to combine everything.
Add water and avocado oil and stir or crumble with your fingertips into small clumps.
Scoop about ⅓ cup of batter into each prepared muffin well. Sprinkle on a small portion of streusel mixture over each muffin.
Bake for 18-23 minutes, until golden brown and a skewer inserted comes out clean.
Allow to cool in the pan for at least 10 minutes before transferring to a cooling rack.
These taste best when served the same day. Bring to room temperature before serving or toast in the oven to crisp up the streusel again.