I used salted butter. You can use unsalted butter, in that case, add a pinch of salt to the frosting.

In a nonstick pan, mix the flour and sugar. Slowly add in the milk and mix. Make sure there are no lumps.

Put the pan on the stove and heat the mixture on medium heat, while stirring continuously.

Soon the mixture will start to boil and thicken. It will have a runny consistency so don't be alarmed if it doesn't seem to be thick enough.

Boil it for 2 more minutes while stirring. Then turn off the stove.

Sieve the mixture using a wire mesh to get rid of any lumps.

Cover the bowl with plastic wrap and refrigerate until completely cooled down. It shouldn't be too cold. The plastic wrap should touch the surface of the mixture or it may form skin on top.

In another bowl, with an electric mixer on medium speed, beat the room temperature butter until light and fluffy.

Add the flour mixture little by little and mix every time until completely incorporated.

And you'll end up with a tasty and smooth frosting. You can add the flavourings at the end according to your choice.