Step 1

Place butter in a 2L microwave-safe jug. Microwave on High for 30 seconds or until melted. Add the flour to the jug. Mix until a smooth paste forms. Add the milk. Whisk to combine. Microwave on High for 2 minutes. Whisk to remove any lumps. Microwave on High in 30-second bursts, whisking in between each burst, for 2-3 minutes or until mixture thickens and boils.

Step 2

Add the cheese. Stir to combine. Microwave on High for 30 seconds or until melted. Whisk mixture until smooth. Season.