Combine the milk and butter in a microwave safe bowl and heat until butter is melted. In a large mixing bowl, combine the milk mixture with the sugar and salt and let cool. In a small bowl, combine the water and yeast and let foam. When the milk mixture is cooled a bit, add the eggs and yeast (the point of the cooling is to not kill the yeast, so don't let it get cold). With a dough hook, mix in the flour. (If using a wooden spoon and elbow grease, mix in the flour and then knead on a floured surface until dough is smooth and soft - about 5-10 minutes). Cover and let rise until double in bulk; about 1-1 1/2 hours. After rising, punch down and divide in half. Roll out on a large jelly roll pan to fit the length of the pan and almost the width. Spread the filling down the middle of each cake and either fold over the outer halves or cut strips and braid it over the filling...it's your call. Sprinkle the streusel equally on top of the two coffee cakes. Cover and let rise another 20 minutes and preheat your oven to 375 degrees. Bake for 25-30 minutes or until golden brown. When cooled, dust with powdered sugar.