Chill the serving glass in the freezer for at least 10 minutes.
Toast the hazelnuts in a dry pan for 3–4 minutes until fragrant, then chop roughly. Melt the chocolate in short bursts in the microwave.
Scoop 2 balls of vanilla ice cream into the chilled glass.
Brew the coffee in the moka pot. Take it off the heat as soon as it starts to gurgle.
Pour the hot coffee straight over the ice cream.
Drizzle with melted chocolate and scatter the hazelnuts over the top.
Serve immediately, while the coffee is still melting into the ice cream.