In a large mixing bowl, whip the butter. Slowly add in 2 cups of powdered sugar. Mix until combined.
Add the vanilla and 1 more cup of powdered sugar and continue mixing. At this point you may need to add a teaspoon or two of milk to thin the frosting down.
Add in your last cup of powdered sugar and mix until combined. Add more or less milk depending on the consistency. You want the strawberry frosting to be thick, creamy and to be able to hold a point.
Fold in the strawberries. If you are wanting to pipe this frosting, I would recommend using freeze dried, so it will become stiffer.
You can use fresh or freeze dried strawberries for this recipe. Using fresh strawberries will make the frosting thinner. If you're wanting to pipe this frosting, I definitely recommend using freeze dried strawberries. Pulse them in a blender before adding to the frosting.