Whip the butter and buttermilk powder until light and fluffy.
Add milk #1 gradually, allowing it to emulsify before adding more.
Incorporate powdered sugar #1 in portions, mixing until fully combined.
Add milk #2 in at least four additions, mixing fully after each.
Taste and adjust sweetness with powdered sugar #2 if desired.
Adjust color with a small dot of purple gel food coloring if needed.
Switch to paddle attachment and mix for 2-3 minutes to smooth out texture.
