Flour Buttercream (Ermine Frosting)

In a non-stick saucepan, add flour, milk and 1 cup of powdered sugar. The mixture will be lumpy.Heat this mixture at medium to low heat. You will need to constantly keep mixing with a whisk or a wooden spoon until everything dissolves and there are no lumps.When the mixture gets thick and starts sticking to your spoon, remove this saucepan from the heat and allow it to cool and come down to room temperature. I place the saucepan in the freezer for 20 minutes so that it cools down quickly.Now... in a deep bowl, add shortening, butter, meringue powder and vanilla extract. Mix until it starts to get a little fluffy.Now, add sugar a little at a time and keep mixing (I add ½ cup at a time).After you have added about 3 cups of powdered sugar, add the flour mixture into this bowl. PLEASE make sure your flour mixture is at room temperature. If it's hot, your butter and shortening will start to melt and it will be a disaster.Mix everything properly again.At this point, taste your frosting to see if you are satisfied with the sweetness. If not, you can add more powdered sugar.And you are done!