Begin by placing four cups of flour in a sizable mixing bowl or stand mixer. Use the back of a spoon to create a hollow in the center of the flour.
Next, crumble fresh yeast or sprinkle dry yeast into the hollow you created in the flour. Pour in lukewarm milk until the hollow is filled, then add a pinch of sugar and mix lightly to combine some of the flour.
Allow the sponge to sit in a warm location for 15 minutes. Once the yeast is activated and has begun to show robust growth, add in the salt, egg, 7 tablespoons of softened butter, and 3/4 cup of sugar to the yeast mixture.
Mix the dough until it becomes smooth and forms a ball. Add up to 1/2 cup of extra flour if required. After forming the dough into a ball, place it in a greased bowl and turn it once before covering it. Let it rise for 15 to 30 minutes.
On a lightly floured board, roll the dough out to a 1/2 inch thickness and transfer it to a 15x10 inch jelly roll pan. Let the dough rest for another 15 minutes while preheating the oven to 375 F.
Using your fingers or the back of a wooden spoon, dimple the top of the dough all over. Mix together the remaining 1/2 cup of sugar and 2 teaspoons of cinnamon and sprinkle it evenly over the dough. Cut the remaining 9 tablespoons of butter into small pieces and spread them evenly over the dough.
Bake the cake for 25 minutes, or until it is done and the sugar/cinnamon mixture has melted together and caramelized slightly. If desired, turn on the broiler for the final 3 minutes of baking, being careful not to burn the topping.
Alternatively, mix 1/4 cup of sugar with enough water (1/4 to 1/2 cup) to dissolve the sugar and brush this sugar water on the hot cake right after you take it out of the oven.
This cake freezes well and can be crisped up in a 350 F oven for a few minutes after defrosting.