Start by making the crème anglaise. Place the milk, cream, half the sugar, and the stem ginger syrup in a saucepan and gently heat to scalding point.
Meanwhile, place the egg yolks, the remaining sugar, and the ground ginger in a bowl and whisk together.
Pour the hot milk mixture over the egg yolks in three batches, stirring constantly. Return the mixture to the saucepan and, over low-medium heat, stir until thick enough to coat the back of a spoon.
Place the chopped blonde chocolate in a heatproof bowl and strain the crème over it. Let it sit for a minute, then gently stir until smooth. Add a pinch of salt, then set aside and keep warm.
For the panettone French toast, whisk together the eggs, milk, and 2 tablespoons of caster sugar. Pour this mixture into a wide shallow bowl and soak the panettone slices for around a minute. They should be well coated but not so soggy that they fall apart.
In a separate bowl, combine the ⅓ cup of caster sugar with the cinnamon and ground ginger. Set aside.
Heat the butter in a frying pan and, once foaming, add the soaked panettone slices. Cook for a few minutes on each side until the outside is crisp and golden. Immediately dredge the slices in the spiced sugar.
To serve, ladle the crème anglaise into four bowls and add a slice of panettone. Finish with a pinch of flaky salt.