By Harry Rutter Sam Smith appeared “smitten” as they made their official debut with boyfriend Christian Cowan, says a body language expert. The Stay With Me hitmaker stepped out with their fashion designer partner at Monday night’s Met Gala in New York City, making their first red carpet appearance as a couple. The pair posed up a storm for snappers, looking lovingly into each other’s eyes in pictures. Exclusively analysing the two’s movements on the red carpet was behavioural professional Judi James, she tells the Mirror that Sam was loving every minute at the glitzy bash, showing the world t…