In a mixing bowl, add the softened unsalted butter. Using your electric mixer, beat the butter on medium speed until it becomes creamy and smooth, about 2-3 minutes.
Add the packed brown sugar to the bowl and continue mixing on medium speed until fluffy, about another 2 minutes.
Pour in the heavy whipping cream and vanilla extract. Beat on low speed until combined, then increase to medium speed and mix for an additional minute.
Gradually add the powdered sugar and salt. Start mixing on low speed to avoid a sugar cloud, then increase to medium speed and mix until smooth and fluffy, about 3-5 minutes.
If the frosting is too thick, add a splash more cream to reach your desired consistency.
Taste your frosting and adjust the flavor as needed by adding more vanilla or a pinch of salt.