In a small saucepan, combine the mashed banana, water, maple syrup, cinnamon sticks, and nutmeg.
Bring to a boil, then reduce to a simmer and simmer for 15 minutes, stirring occasionally.
Remove from the heat and stir in the vanilla.
Strain the mixture through a fine mesh sieve, and pour the banana bread syrup into an airtight glass container. This mixture can be kept in the refrigerator for 5 to 7 days.
Make the latte:
Add the water to a small glass or bowl. Spoon the matcha powder through a fine mesh sieve to break up any clumps.
Whisk the matcha into the water in a front-to-back motion until slightly frothy on top.
Add ice to your serving glass. (Note, this can also be served hot; just use hot water.) Pour in the matcha and top with milk of choice.
Add 1 to 2 tablespoons of banana bread syrup. Sip and enjoy!