Prepare a large bowl or a Cambro, spraying it lightly with cooking spray or brushing a thin layer of oil. Set aside.
To make the dough
Place the flour, 70 grams (⅓ cup) sugar, and fine kosher salt in a stand mixer fitted with the paddle attachment. Stir them together for a few seconds on low just to get everything evenly mixed.
In a small bowl, place the warm water (the temperature of the water should be around 38–40 ºC or 100 ºF). Stir in the ⅛ teaspoon of sugar and sprinkle the yeast over top. Stir everything together and let rest for 10 minutes. The mixture should develop a thick foam on top.
When all the components are ready, add the milk and butter mixture to the dry ingredients, along with the foamy yeast mixture and the two eggs. Stir them together on low speed to form a shaggy, evenly mixed dough.
Add the raisins and mix them in, then turn off the mixer, cover the bowl with the towel and let the dough rest for 10 minutes.
Switch to the hook attachment to begin kneading on low speed. If the dough seems too wet, add up to 30 grams (¼ cup) of all purpose flour. The dough should not be so sticky and it shouldn't stick to the bowl. It should feel tacky.
Knead the dough for 10 minutes in the mixer, then dump it out on the counter and knead it by hand for a minute or so to form a smooth round ball of dough.
Transfer the dough to the greased bowl, cover with a towel or plastic wrap, and let it rise until doubled in size (for about 45 minutes to an hour).
To make the filling
In a bowl, cream together the softened butter, the sugars, and the cinnamon until you have a thick brown paste. Set aside.
Assemble the rolls
When the dough has risen, remove the towel. Lightly flour your counter and transfer the dough to roll it out into a big rectangle of at least 12x16 inches (don't worry too much if it's bigger or smaller).
Spread the filling over the entire surface of the dough, then roll tightly into a long 12 inch log.
Cut the dough into 12 equal buns (you don't have to trim the ends) and place them in the prepared baking pan. Cover with plastic wrap or a towel.
Let the rolls rise
Let the rolls rise until they have puffed and until proofed (if you lightly press your finger into the side of a roll, the indent should very slowly fill out and disappear).
Preheat the oven to 350 °F (175 °C).
Bake the buns until golden brown and internal temperature is at least 190 °F (88 °C) measured with an instant-read thermometer. This takes about 25 to 30 minutes.
Make the frosting
Cream together the cream cheese, icing sugar, and milk. Use a spatula to make sure to mash any lumps of cream cheese.
Dollop a little spoonful of icing on each bun and use an offset spatula (or the back of a spoon), spread the frosting on the top. Serve warm.
Notes
Feel free to double the cream cheese icing if you want more frosting!