In saucepan, combine heavy cream, milk, thai tea concentrate, and pinch of salt over medium low heat. Bring to a simmer and remove from heat.
In a bowl, whisk together sugar and egg yolks until well combined.
Slowly pour half of the hot cream/milk mixture into the eggs and sugar, whisking while you do.
Pour the contents of the bowl back into the saucepan, place over low heat and stir with a rubber or silicone spatula.
Cook for about 5-7 minutes, until custard has thickened and reaches a temperature of about 175°F.
Pour into a bowl or container to chill.