Remove the lavender fudge from the refrigerator to sit at room temperature while the caramel is prepared. In a small bowl mix together the finishing salt and lavender for the top of the caramel; set aside.
Place sugar in a heavy saucepan over medium-high heat. Allow sugar to warm until it begins to melt (approximately 5-8 minutes). Begin to stir the sugar to hasten melting and ensure no burning; stir until fully liquefied (approximately 10-12 minutes from starting to heat the sugar).
Reduce heat to medium and add the butter. It will splatter to be careful to avoid getting burned. Stir to fully melt and incorporate the butter.
Slowly drizzle the cream into the caramel mixture, again it will splatter. Stir to fully mix together. Remove from heat and allow to cool only for 3 to 4 minutes (if it cools longer it will begin to set and not spread on top of the fudge).
Spread the caramel on the top of the fudge quickly smoothing it evenly over the top. Quickly sprinkle the salt and lavender mixture on the top of the fudge before it sets. Return to the refrigerator to set for a few hours.
Remove the fudge from the refrigerator to cut it. Lift the fudge in the foil out of the 9 x 9 pan. The caramel top will be firm but can be cut and will soften when at room temperature. Cut the fudge into ¾ inch by ¾ inch pieces. I found this is most easily done but cutting a strip of ¾ inch wide fudge and then cutting it into pieces. Wrap in candy foil or serve straight away!