This old-fashioned frosting, also called boiled-milk frosting, is firm like buttercream but light and airy like whipped cream.
The flour/milk mixture can be made up to 2 days ahead; just make sure to follow directions on covering and chilling.
Whisk milk and flour together in a saucepan. Cook over medium heat until thick and smooth, about 5 minutes, whisking often.
Boil 1 minute to eliminate the starchy taste of the flour, whisking constantly. Transfer to a bowl and cover with plastic wrap, pressing it on the surface to prevent a skin from forming; chill until cold.
Cream sugar and butter in a bowl with a mixer on high speed until light and fluffy, about 5 minutes. Add coconut flavoring and chilled milk mixture, beating to the consistency of whipped cream, about 5 minutes.
% Daily Value*
Total Fat 30g 46%
Saturated Fat 19g 95%
Cholesterol 80mg 26%
Sodium 20mg 0%
Carbs 28g 9%
*Percent Daily Values are based on a 2,000 calorie diet.