Preheat the oven to 350 degrees.
Combine the oats with the milk and let soak for five minutes. Meanwhile, combine the flours, baking powder, baking soda, salt, and spices.
In a separate bowl, beat together the butter and sugar, and then beat in the egg.
Gently stir together the oat-milk mixture with the dry ingredients, then fold in the butter-sugar mixture. Stir in the blueberries and chocolate chips, being careful not to overmix.
Line a muffin pan with liners. Divide the batter amongst 12 muffin tins, filling about 3/4 of the way.
Combine the flour and brown sugar for the crumble together and then pour the melted butter on top. Use a fork to mix into a crumble, and then sprinkle evenly on top of the muffins.
Bake for 16-18 minutes or until an inserted toothpick comes out clean.