Preheat your oven to 375. Either line your muffin pan with liners, or spray well with non-stick spray.
Mix the brown sugar and eggs together. Add in wet ingredients, mix well then add in the remaining dry ingredients. Mix it together well.
Evenly pour into your muffin tin. Set this aside. And mix together the crumble for the top.
Using a fork mix the dry ingredients. Pour the melted butter in and mix well, it will crumble on its own, just mix it together with your fork.
Sprinkle, or dump some of the crumble on top of each of the muffins, press it down into the batter. The more crumble you add the more your coffee cake will have, the better it will taste!