Place coconut, cornstarch, sugar, egg whites and extract in a heatproof bowl and mix well.
Set the bowl over a pot of boiling water (or use a double boiler). Heat, stirring until the mixture thickens, then remove from heat and set aside, about 4 minutes.
Scoop out macaroons, about a scant tablespoonful, and place on ungreased baking sheet.
Bake at 350 degrees F for 10 to 15 minutes or until lightly golden but still soft and chewy. Remove to a wire rack to cool.
If dipping in chocolate: Place chocolate in a small microwave-safe bowl and heat on HIGH power for 1 minute. Stir until smooth, microwaving in additional 15 second increments if needed. Then, dip bottoms of cookies in chocolate, allowing excess to drip back into bowl. Place on a parchment or waxed paper lined baking sheet in refrigerator to set.