Traditionally mirror glaze was used to cover mousse cakes (called entreme), petite gateaux and tarts. Now people are using them to cover all manner of cake and dessert. Or even as a garnish - such as the drip on a drip cake.
Those desserts in the cup things, what are they called….so many names come to mind. Technically they are called verrines which means….a small glass, jar, bowl, acrylic tube (you get the idea) containing layers of food