ISO: sticky carrot muffins

I am looking for the sugary mixture that goes at the bottom of a pan of cinnamon buns. You smear this mixture at the bottom of muffin tins and then add the carrot muffin batter. When baked, you turn the muffins out upside down. They are superb. I tried mixing butter, brown sugar, vanilla, and cinnamon together but it just stayed sugary at the bottom, it didn't melt. They are not gooey like cinnamon buns, this mixture just adds a good texture. Anyone who baked in a bakery would know this mixture. They usually make a big batch and store it in the fridge and smear the bottom of the tins. Thank you.