Add the active dry yeast to the warm milk. Let it sit for 5 minutes.
In the bowl of a stand mixer fitted with the dough hook, add the flour, butter, sugar, salt, and yeast mixture. Mix for 4-5 minutes until a dough forms and the dough pulls away from the sides of the bowl.
Spray the inner pot of the Instant pot with cooking spray or oil. Add the dough to the Instant Pot and close the lid. Set the Instant Pot to "yogurt" for 90 minutes.
After 90 minutes, open the lid of the Instant Pot and place the dough on a lightly floured surface. Roll the dough into a thin sheet, about 12 inches by 10 inches.
Spread the softened butter all over the dough. Mix the brown sugar and cinnamon sugar together and then sprinkle it over the dough. Roll the dough into a log and cut it into 8 equal pieces.
Butter a springform pan and add the 8 pieces to the springform pan. Cover it with aluminum foil. Add 1 ½ cups to the bottom of the Instant Pot and set the trivet insert into the pot. Add the springform pan and close the Instant Pot. Set the Instant Pot to 30 minutes on high pressure.
While the cinnamon rolls cook, mix the icing ingredients together and set that aside.
After 30 minutes, let the Instant Pot naturally release for 10 minutes. Remove the pan from the Instant Pot and remove the aluminum foil. Remove the outer ring of the pan. Spread the icing over the cinnamon buns and enjoy!