For the syrup
Combine the water, sugar, cinnamon, vanilla, maple syrup and salt in a small saucepan and bring to a simmer over a medium heat. Simmer for a few minutes, stirring, until all the sugar dissolves.
Allow the syrup to cool to room temperature.
Divide the syrup between two glasses and top with the frothed oat milk. Pour the warm espresso in slowly to achieve a latte look.
The drink can also be served cold with ice cubes and cooled espresso.