1. Melt the butter in a saucepan and add the flour.
2. Cook, stirring, for 2 minutes, then gradually stir in the milk.
3. Bring to the boil and simmer, still stirring, until thickened.
4. Add the cheese and stir until it melts and the sauce is smooth.
5. Use a coating cheese sauce to cover fish, eggs, meat, vegetables, etc.