Step 1: Toast the black sesame seeds. Heat a dry, non-stick pan over medium-low heat. Add the black sesame seeds and toast for 3-5 minutes, stirring frequently, until fragrant and slightly shiny. Be careful not to burn them. Immediately transfer them to a plate to cool.
Step 2: Grind the toasted sesame seeds. Once cooled, transfer the toasted black sesame seeds to a high-speed blender, spice grinder, or food processor. Add 2 tablespoons of the milk and 1-2 tablespoons of honey/maple syrup. Blend until a thick, smooth paste forms. You may need to stop and scrape down the sides occasionally. This paste is the heart of your Black Sesame Latte.
Step 3: Heat the milk. In a small saucepan, gently heat the remaining 1.5 cups of milk over medium heat until it's hot but not boiling. If you have a milk frother, you can use it to heat and froth your milk simultaneously for a creamier Black Sesame Latte.
Step 4: Combine the ingredients. In your serving mug, add the black sesame paste (1-2 tablespoons, depending on desired strength) and the vanilla extract, if using. Pour a small amount of the hot milk over the paste and whisk vigorously until the paste is fully dissolved and incorporated into the milk, forming a smooth, dark liquid.
Step 5: Finish and serve. Pour the remaining hot milk into the mug, stirring gently. If you frothed your milk, spoon the foam over the top. Garnish your Black Sesame Latte with a sprinkle of extra black sesame seeds or a tiny drizzle of honey. Enjoy immediately!