Chill a can of full-fat coconut milk in the refrigerator for at least 4 hours and chill your mixing bowl and whisk in the freezer for about 15 minutes.

Open the chilled coconut milk can and scoop out the thick cream at the top, discarding the watery part.

Whip the coconut cream on medium speed until stiff peaks form, taking about 3-5 minutes.

Gradually sprinkle in the unsweetened cocoa powder and sweetener, mixing on low speed until fully combined for about 1-2 minutes.

Fold in vanilla extract and instant coffee if desired, combining gently with a spatula.

Spoon the mousse into dessert cups for immediate serving or refrigerate for 1-2 hours for a thicker texture.