Cut up the leeks into 5-cm lengths. Boil and drain them, then keep them in a cool place on kitchen paper.
Heat the liquid honey, add the turmeric, ground coriander, cumin seeds, mustard and vinegar. Reduce for 1 minute. Whip up the sauce with 125 g diced cold butter. Season to taste, add the grated lemon rind, and keep warm.
Reheat the leeks in a steamer. Serve onto warm plates and top with the sauce. Heat the remainder of the butter and, when it is browned, drizzle onto the leeks. Decorate with flower petals and herbs.
Suggested garnishes: yellow and violet pansy petals, herbs, gooseberries.