Brew 1.5 cups of strong espresso or very strong drip coffee. If using instant espresso concentrate, dissolve it in 0.25 cup cold water to make a concentrated coffee and chill.

Place 1 cup of ice cubes into a large cocktail shaker or pitcher. Pour the brewed coffee over the ice to chill it rapidly; set aside while you prepare the banana syrup.

Banana syrup / flavoring

Make quick banana syrup

In a small saucepan combine mashed ripe banana, 2 tbs granulated sugar, and 2 tbs water. Add 0.5 tsp lemon juice. Cook over medium-low heat, stirring frequently, until the sugar dissolves and the banana breaks down into a saucy consistency, about 3–4 minutes. Do not boil vigorously; you want a syrup-like mixture.

Remove from heat and stir in 1 tsp vanilla extract. Let the mixture cool slightly (5–10 minutes). For a smooth syrup, transfer to a small blender or use an immersion blender and puree until smooth. Optionally strain through a fine-mesh sieve to remove fibers for a silky syrup. This yields about 3–4 tablespoons of banana syrup.

Milk & finishing

Assemble the iced banana latte

In the chilled cocktail shaker or pitcher with the coffee and ice, add 3 tbs of the prepared banana syrup (adjust to taste). Pour in 1 cup cold milk and 2 tbs cold heavy cream if using. Secure the shaker lid and shake vigorously for 10–15 seconds to combine and create a light froth. If using a pitcher, stir energetically or use a milk frother briefly.

Strain the latte into a tall glass filled with fresh ice (discard the coffee-ice used to chill earlier or use as desired). If you prefer more banana flavor, spoon an extra 1 tbs syrup into the glass before pouring.

Garnish with banana slices on the rim and a light dusting of brown sugar or cinnamon (about 1 tsp) on top. Serve immediately with a straw.