Faux Tart with Instant Lemon Ginger Custard

I was at Palena, my favorite restaurant in Washington, at the end of a meal, when the dessert's taste and texture made me gasp. It was a shallow lemon custard, not just silky but crystal clear in its flavor: a blast of just lemon, cream, and sugar in one bite. Pastry chef Aggie Chin explained that it's her take on a posset, a traditional English dessert in which the cream softly sets with nothing but the help of the acid from the lemon juice. I knew I'd try this at home. It makes the perfect topping for the cookie-crumble crust I like to make, and the perfect base for the fruit I like best with lemons: berries. This can be easily doubled when you'd like to make dessert for two nights in a row, or for you and a friend to share.