Make the strawberry powder by placing the freeze dried strawberries into a food processor. Grind up the strawberries until they are a fine powder. Some seeds and bits of strawberry will still be in the powder which is okay.
In the stand mixer, cream the unsalted butter until it is lighter in color and fluffier.
Add in the powdered sugar, a third of a cup of powdered freeze dried strawberries, the vanilla extract, and two tablespoons of milk. Use the rubber spatula to mix the ingredients together a bit before covering the stand mixer and mixing on low until creamy.
If the strawberry buttercream is too stiff for what you need to frost, add more whole milk and mix on low.