Lightly grease six 125ml (1/2 cup) moulds with a little oil. Place the sesame seeds in a non-stick frying pan over medium heat. Cook, stirring, for 2-3 minutes or until lightly toasted. Set aside to cool. Transfer seeds to a small food processor or electric coffee grinder. Process until coarsely ground.
Combine ground seeds, milk, maple syrup and vanilla bean in a saucepan. Stir over low heat until the mixture almost boils. Remove from heat and set aside for 5 minutes to infuse. Remove vanilla bean.
Meanwhile, place the gelatin and boiling water in a small heatproof bowl. Stir until the gelatin dissolves. Pour the gelatin mixture into the milk mixture. Stir to combine. Add the cream. Stir to combine.
Pour the mixture through a fine sieve into the prepared moulds. Place in the fridge for at least 4 hours or overnight to set.
To make the toffee crisp, line a baking tray with baking paper. Place all the sesame seeds in a small non-stick frying pan over medium heat. Cook, stirring, for 2-3 minutes, until lightly toasted. Remove and set aside. Add the maple syrup and 1 tbs water to the pan. Bring to a simmer over medium heat. Reduce heat and simmer for 5-6 minutes, until thickened slightly. Remove from the heat and set aside until the bubbles subside. Pour the toffee onto the prepared tray and sprinkle with the toasted seeds. Set aside to cool. Break the toffee into pieces.
Gently turn the panna cotta out onto serving plates. Top with toffee crisp and drizzle with extra maple syrup.