White Chocolate Champagne Buttercream

Heat the milk, champagne and sugar in a heavy-bottomed pan over medium-low heat until the sugar is dissolved, about 15 - 20 minutes. Remove from heat, sift in the flour and whisk until the flour is completely absorbed. Pour into the bowl of a stand mixer fitted with the paddle attachment and mix on medium-low until the outside of the bowl is cool to the touch. Meanwhile, cut each stick of butter into at least eight pieces. Add the vanilla, heavy whipping cream and the butter to the cooled mixture. Mix on low to combine the ingredients. Very slowly increase the mixer speed until you reach medium-high. (If you do this too quickly you'll end up wearing what's in the mixer.) The buttercream may look curdled along the way, but just keep beating. Beat the buttercream for 7 - 10 minutes until creamy. Lower the speed to medium and slowly drizzle in the melted white chocolate. Mix 1 - 2 minutes to fully incorporate the white chocolate. Use immediately or refrigerate/freeze. Thaw frozen buttercream in the refrigerator. Allow refrigerated buttercream to come to room temperature and then rebeat before using. Makes about 1-1/2 quarts.