In a stand mixer (or with a hand mixer) combine all cake ingredients and beat until smooth. Using a cookie scoop, add to lined muffin tins.
In a small bowl, combine the ingredients for the streusel topping. Using a spoon, or your fingers, sprinkle over the batter until all of the topping has been used.
Bake for 13-15 minutes (for mini muffins). Larger muffins will require more baking time.
Let cool for 15 minutes in the pan, then remove to a rack to cool completely.