Make the Flour Paste:
In a medium saucepan, whisk together the milk and flour until no lumps remain.
Cook over medium heat, whisking constantly, until the mixture thickens into a smooth, pudding-like paste. This usually takes about 5-10 minutes. Be patient and keep whisking to prevent burning.
Once thickened, remove from heat and pour the paste into a clean bowl.
Cover the surface of the paste with plastic wrap, pressing it directly onto the surface to prevent a skin from forming.
Let the paste cool completely to room temperature. This is crucial! You can speed up the cooling process by placing the bowl in the refrigerator for 1-2 hours, but make sure it’s fully cooled before proceeding.
Make the Frosting:
In a large mixing bowl, beat the softened butter with an electric mixer until light and fluffy. This should take about 3-5 minutes.
Gradually add the sugar to the butter, beating until the mixture is smooth and creamy.
Once the flour paste is completely cooled, add it to the butter and sugar mixture.
Beat on medium speed until the frosting comes together. It might look curdled at first, but keep beating! It will eventually become smooth and fluffy. This can take several minutes.
Add the vanilla extract and beat until combined.
Frost and Enjoy!
