Step 4
Meanwhile, in large bowl or bowl of a stand mixer fitted with the paddle attachment, add room temperature butter and beat on medium speed for 2-3 minutes, until fluffy and light. Then begin adding powdered sugar, 1/2 cup at a time, ensuring all sugar is fully incorporated prior to adding the next 1/2 cup. Once all the powdered sugar is added, add the blackberries and a pinch of salt. Continue to mix for another 3-4 minutes, until light and fluffy.