Start by brewing two shots of espresso using an espresso machine or make strong coffee using your preferred method. Set it aside to cool.
You can purchase ready-made white chocolate sauce from the store or easily make it home by melting good quality white chocolate with a bit of milk over low heat until smooth. Start with 1 cup of white chocolate chips and add 1/2 cup of milk. Heat on low to medium heat until the chocolate is melted. Allow it to cool before using.
Take out the chilled milk (or milk alternative) from the refrigerator and pour it into a separate tall glass. Pour in the cooled espresso/strong coffee (2 espresso shots equal 4 oz of water, so if you opt for instant coffee, dissolve the coffee in 4 oz cold water). Add two tablespoons of prepared white chocolate sauce/syrup.
To achieve that classic Starbucks presentation, either cover the glass with a lid and shake it vigorously for 10-15 seconds or use a long spoon to stir everything together thoroughly. Add 3/4 cup ice in a serving glass. Pour the coffee mixture over the ice cubes.