Spray a 23 cm x 23 cm baking pan with cooking spray. Line the pan on the bottom and sides with parchment paper, pressing it into the oil. Set aside.
Place dates, peanut butter, vanilla, cocoa powder, and espresso powder in the bowl of a food processor. Blitz for 2-3 minutes or until smooth. Spread the mixture into the lined pan evenly.
Place chocolate in a heatproof bowl over a small saucepan of simmering water to melt, stirring occasionally. Pour the melted chocolate over the fudge mixture and spread evenly. Sprinkle the top with chopped peanuts. Place the fudge in the refrigerator to firm (at least one hour) before cutting and serving. For best results, cut with a hot knife.
Store in an airtight container in the refrigerator.