How to Make It
In a food processor, pulse the olives with the olive oil until finely chopped. Scrape into a small saucepan and cook over moderately low heat, stirring occasionally, until the oil separates and the mixture looks broken, 2 to 3 minutes. Transfer the tapenade to a small bowl. Clean the food processor.
In the food processor, puree the feta until smooth. Transfer to a small bowl. To serve, spread the feta on crackers and top with the smoked trout, broken tapenade and arugula.