In a small saucepan, sprinkle gelatin over milk; let stand for 1 minute. Heat over low heat, stirring until gelatin is completely dissolved. Add cocoa and coffee; stir until dissolved. Transfer to a small bowl; refrigerate until mixture begins to thicken.
Beat until light and fluffy. Combine yogurt and sugar; beat into gelatin mixture. Fold in whipped topping. Divide between two dessert dishes. Refrigerate until firm.