Whisk warm milk, yeast, and sugar together in the bowl of a stand mixer. Cover and allow to stand for 5 minutes. Fit mixer with dough hook.
To yeast, add eggs, butter, salt, and 1 cup flour. Beat on low speed for 30 seconds to combine, scrape down the sides of the bowl. Add remaining flour and beat on medium speed until the dough comes together and pulls away from the bowl; about 2 minutes.
Knead another 2 minutes in the mixer or can be done by hand on a lightly floured surface.
Lightly oil a large bowl and place the dough, turning to coat on all sides. Cover the dough and allow to proof in a warm spot until doubled; 1 - 2 hours.
Generously spray a 10-12 cup bundt or tube pan.
Prepare coating by putting 1/2 cup melted butter in one bowl and sugar/cinnamon mixture in another. Depending on how heavily the balls of dough are coated, more sugar/cinnamon mixture may be required.
Deflate dough and pull together in a ball. Taking small equal amounts, roll into 1 1/4" balls, 40 to 45 in total. Working one at a time, roll balls in butter then sugar/cinnamon mixture and place in the pan. When 1/3 completed, sprinkle half of your prepared layering ingredients evenly. Repeat once more then finish with a final layer of dough balls. Cover the pan and allow it to rest for 20 minutes.
At this point, you can refrigerate it to bake in the morning or continue with the recipe.
Preheat the oven to 350°F and adjust the rack to bake in the bottom third.
From the coating list, melt the remaining butter and whisk in brown sugar and vanilla. Pour evenly over the top of your prepared dough.
Bake for 35-45 minutes, until golden brown. Cover loosely with foil if browning too quickly. Cool for 5-10 minutes and then invert on a serving plate.
For icing: Whisk all ingredients together and drizzle over the warm bread. Chocolate or caramel work well also.