Heat ghee in a pan, add jowar flour and mix well.
Sauté the flour on medium flame till it turns light brown and leaves a nice aroma, which should take around 2 minutes.
Add milk, mix well, and cook on medium flame for about a minute. Keep stirring to ensure that no lumps form in the mixture.
Add about half cup water and cook for another minute or so, while stirring continuously.
Add jaggery and mix it properly.
After jaggery melts, add mashed banana, give the mixture a good stir, and then turn off heat. (Remember you mustn't cook milk and jaggery together for too long otherwise the milk will curdle.)
You can add some more milk to the sheera if required to get the desired consistency, depending on your baby's age.