Slit the cardamom pods, if using, and extract seeds. Heat the cardamom seeds or the lavender with the milk, bringing slowly to the boil.
Whisk together the honey and egg yolks in a bowl and pour on the boiling milk, stirring constantly. Set the bowl over a pan of simmering water, making sure that the base does not touch the water. Stir for about 5 minutes, until the custard thickens and