We slept in this morning which is unusual for our family. When I got up to fix breakfast I wanted to fix something special. What started as Blueberry Streusel Muffins ended up as a Cinnamon Streusel Coffee Cake. Don't ask me how blueberry muffins morphed into coffee cake but the result was delicious and won a thumbs up from everyone.
Heat oven to 375°. Grease 9 x 9 inch baking dish. Prepare Streusel Topping. Beat egg slightly in medium bowl; stir in remaining ingredients until moistened. Pour into greased baking dish; sprinkle with topping. Bake until golden brown, 18 to 25 minutes.
While the cake is baking, make the glaze. In a bowl, mix the powdered sugar, milk, and vanilla until glaze is of desired consistency. When the cake comes out of the oven, immediately pour glaze onto the hot cake. Let the cake sit for a few minutes os the glaze can set. Serve warm or room temperature.