
In a saucepan, combine water, brown sugar, mashed banana, cinnamon stick, and salt. Simmer for 8-10 minutes until mixture thickens. Discard cinnamon stick.
Blend the syrup until smooth and stir in vanilla extract. Cool in a Mason jar.
Fill a glass with ice. Add banana bread syrup, espresso, and milk.
Shake banana bread syrup and heavy cream in a sealed container until thickened. Pour over latte and garnish with cinnamon or nutmeg if desired.