Custard without the cream? We'll take it. Especially when it's laced with an exotic hint of cardamom, a spice that does more to transport us across the globe than any other we know.
In a blender, process cashews, 2 cups milk, salt, and syrup for 1 minute. Transfer mixture to a saucepan, add cardamom, and bring to a boil, whisking. Reduce heat and simmer, covered, 15 minutes.
In a bowl, whisk remaining tablespoon milk and the arrowroot until smooth. Add to saucepan and thicken mixture over medium heat, whisking, 30 seconds. Remove from heat and stir in vanilla.
Strain custard into a bowl and let cool slightly, then transfer to refrigerator. Serve chilled.