Mix Insta-Bake and sugar in a large bowl and cut in butter until crumbly. Add egg and milk, mix gently just until no dry bits remain.
Spread half of batter in prepared pan and top with half of prepared streusel(see below). Spread remaining batter on to and sprinkle evenly with remaining streusel. Bake 25-30 minutes, or until wooden pick comes out clean.
Streusel topping: Combine and mix all streusel ingredients with a fork until crumbly.
Variation: Sour Cream Coffee Cake ~ Reduce milk to1/2 cup and add 3/4 cup sour cream to the basic Streusel Coffee Cake recipe.