Pre-heat the oven to 190C (170C fan forced)
Either grease a muffin tin or line the tin with muffin liners.
Combine the ingredients for the topping in a small bowl and set aside.
Place the ingredients for the dry mix in a small bowl, stir to combine and then set aside.
Put the melted butter, rapadura sugar and blackstrap molasses in a large bowl, and stir together until combined.
Mix the milk, eggs and vanilla extract into the butter and sugar.
Add the dry ingredients to the wet ingredients, and stir together. I use a large spatula to do this, making cutting motions through the mix until they are combined. Do not over-mix the batter or your muffins will be tough.
Divide the mixture between the muffin liners.
Sprinkle the topping mixture over the muffins.
Bake the muffins for 15 - 20 minutes, or until well risen and firm. They will look dark brown due to the natural sugars and flours. If you are unsure whether they are ready, insert a skewer into one. The skewer should be clean when removed.
Remove the tin from the oven and allow to stand for 5 minutes before removing them from the tin and cooling them on a rack.
The muffins can be served immediately. They can be kept at room temperature for 1 day and refreshed in the microwave or oven for eating, or frozen for up to three months.