Bring 8 fl oz of water to just below boiling. Stir the 2 instant espresso packets into the hot water until fully dissolved to make a strong coffee concentrate. Let it cool for 2–3 minutes while you prepare the glasses.
If you want extra chill and crisper layers, pop the clean serving glasses in the freezer for 2 minutes. Meanwhile, measure the vanilla syrup so you have about 1 1/4 oz per glass.
Divide the vanilla syrup between the two glasses, pouring it into the bottom of each. Add about 1 1/2 cups of ice to each glass (fill to your preference).
Pour the milk evenly into the glasses over the ice. To keep the layered look, pour straight down the side of the glass rather than splashing through the ice.
Slowly pour the warm-ish espresso concentrate down the center of each glass. Pouring slowly from a low height helps the dark espresso sit over the milk and create the classic macchiato layers.
Top each drink with a dollop of whipped cream if using. Drizzle 1 tbsp of salted caramel sauce over the cream (or directly on the drink) and finish with a tiny pinch of flaky sea salt for contrast.
Serve immediately. If you prefer a less sweet drink, stir gently before drinking to distribute the syrup and espresso.