Step 5
Meanwhile, to make the frosting, in the bowl of a stand mixer fitted with the whisk attachment (or a large mixing bowl using a hand mixer and the whisk attachment), beat the butter until smooth and creamy, about 1 minute. Add the powdered strawberries and turn the mixing speed on low. Gradually add the powdered sugar along with the raspberry puree, white chocolate, whole milk, vanilla extract, and salt. Turn to mix speed up to high and beat for 3 minutes until fluffy. Chill in refrigerator for 15 minutes before using.