Chill the cream or coconut milk and place a large mixing bowl in the refrigerator until cold. A cold bowl helps the mixture thicken into glossy ripples instead of staying loose.

If using full-fat coconut milk, scoop out only the firm coconut layer from the top of the can and leave the watery liquid behind. The solid coconut cream should feel dense and creamy rather than pourable.

Beat the chilled cream or solid coconut cream with a stand mixer or electric hand mixer until stiff peaks form. The beaters should leave sharp trails, and a lifted peak should stand upright with little to no curl at the tip.

Sift in the cocoa powders and sweetener, then add the optional vanilla and instant coffee. Sifting prevents dark cocoa pockets and sweetener lumps from hiding in the airy cream.

Mix on low speed only until the mousse looks evenly chocolatey and smooth. Stop when the mixture holds its ridges and feels thick but still light on the spatula.