Preheat oven to 350°F (175°C) and line a muffin tin with paper liners.
In a large bowl, cream together the sugar and softened butter until fluffy.
Beat in eggs one at a time, then add milk and vanilla extract, mixing well.
In another bowl, whisk flour, baking powder, and baking soda together.
Gradually add dry ingredients to wet ingredients and mix until just combined.
Prepare streusel topping by combining brown sugar, cinnamon, cubed butter, and flour; mix with a fork until crumbly.
Fill muffin liners two-thirds full with batter and sprinkle streusel topping evenly on each.
Bake for 18 to 20 minutes or until a toothpick inserted in the center comes out clean.
Cool muffins in the pan for 5 minutes, then transfer to a wire rack to cool completely.