Preheat oven to 350ºF.
For the batter, in a medium bowl, whisk together Bisquick, sugar, milk, and egg just until blended.
For the streusel, in a separate bowl, whisk together Bisquick, brown sugar, and cinnamon. Grate the butter into the streusel and fold gently until coated.
Butter a 1 quart dish or square pan, pour in the batter, and evenly distribute the streusel. Pierce the streusel into the batter.
Bake 20-22 minutes. Cool 5 minutes before serving. *This recipe can be doubled in a 9"x9" square pan or tripled in a 13"x9".