Fill glass with ice: Fill a tall glass or wide-mouth mason jar generously with 1 ice cubes.
Brew espresso: Brew 1 espresso shot (freshly brewed) fresh using an espresso machine, Moka pot, or pod machine on its most concentrated setting.
Add milk & cinnamon: Pour 4 fluid ounces milk of choice over the ice. Optionally dust 0.3 teaspoons ground cinnamon (for milk layer, optional) over the milk and gently stir to incorporate.
Pour espresso: Slowly pour the hot espresso over the back of a spoon onto the cold milk and ice to create a beautiful swirl effect.
Make honey cream: In a small jar or frother cup, combine 3 fluid ounces heavy cream or oat-based heavy cream, 1 fluid ounces pure honey (wildflower, clover, or raw), 2 fluid ounces milk of choice (for honey cream), and 1 pinch of kosher or fine sea salt. Froth with a handheld frother until slightly thickened, foamy, and pourable — not stiff.
Pour honey cream on top: Slowly pour the frothed honey cream over the back of a spoon onto the surface of the drink so it floats as a distinct golden layer.
Finish & serve: Dust 0.3 teaspoons ground cinnamon (for finishing) over the honey cream. Serve immediately with a straw so each sip pulls cold coffee up through the creamy top layer.