A low-effort dessert inspired by cafe de olla, which is a drink I consumed daily while on holiday in Oaxaca, Mexico. It's a black coffee gently spiced with cinnamon and cloves, and sweetened with piloncillo (an unrefined sugar). Here, I've turned it into something refreshing for summer, using dark brown sugar instead, not least because it's easier to find. I can never resist a post-dinner coffee, and this scratches both that caffeine and sugar itch.