Set aside 2 tablespoons of chocolate chips for garnish. Pour about 2 tablespoons of the milk into a small microwave-safe cup and warm for 8–12 seconds until just warm (not boiling).
Whisk the instant coffee and hot cocoa mix into the warmed milk until dissolved and smooth — this concentrated mocha warms the flavor without using brewed coffee.
In a blender add the remaining milk, the dissolved mocha concentrate, 1/2 cup chocolate chips (reserve the garnish), chocolate syrup, simple syrup, vanilla, and a pinch of sea salt.
Add the ice on top. Pulse the blender 4–6 times to break up the ice, then blend on high for 45–60 seconds until velvety. If mixture is too thick, stop and add 1–2 tablespoons of milk; if too thin, add a few more ice cubes and pulse.
For little chocolate nuggets, give the blended drink one quick low-speed pulse with the reserved 2 tablespoons of chips (this folds in tiny pieces without fully pulverizing them).
Drizzle chocolate syrup inside two tall glasses for a pretty swirl, pour the frappuccino evenly between them, top with a generous swirl of whipped cream and extra chocolate chips, and finish with more chocolate syrup if you like.
Serve immediately with a wide straw. If you want a stiffer texture, pop the blended frappuccino in the freezer for 3–5 minutes before serving.