In a small bowl, dissolve yeast in a ¼ cup of the hot milk and set aside.
In a large bowl mix milk, sugar, melted butter, salt and egg.
Add 2 cups of flour and mix until smooth. Add yeast mixture. Mix in remaining flour until dough is easy to handle.
Knead dough on a lightly floured surface for 5 to 10 minutes. Place in an oiled bowl, cover and let rise until doubled in size, usually 2 - 3 hours.
To make the filling:
Add flour and mix with a fork until moist clumps form. Set aside.
When doubled in size, punch down dough.
Roll out on a floured surface into a 15 by 9-inch rectangle.
Spread melted butter all over the dough. Take 1/2 the filling mixture and crumble over the rolled dough.
Beginning at the 15-inch side, roll up the dough and pinch edge together to seal. Cut into 10 - 12 slices.
Coat the bottom of a 13×9 pan with melted butter. Place the in the pan leaving at least an inch between them. Brush them with melted butter and crumble the remaining crumb mixture over and between the buns.
Let rise again until the buns are doubled in size (about 45 minutes to an hour).
Bake on 350f/175c for 25 - 30 minutes or until golden brown.
Meanwhile, In a mixing bowl whisk together 2 tablespoons of the milk, the melted butter powdered sugar, and ½ tsp vanilla extract.
Add in more milk as needed 1 teaspoon at a time until it is the desired consistency.