1 C shortening
1 C butter
1 tsp vanilla
2 lb (8 C) powdered sugar
3 Tbsp milk
1/2-1 tsp grated lemon rind (optional)
1-2 Tbsp squeezed lemon juice (optional)
Mix together (you want to beat it together until it's nice and fluffy) and spread on cooled cinnamon rolls.
I felt it needed a little something, so I added some lemon rind and juice. I thought it made it super awesome, but Bec preferred the original.