Preheat oven to 180°C (160°C fan). Butter and flour 6 mini-angel food cake pans or jumbo muffins pans, shaking well to discard excess flour. Pick the tops off the thyme sprigs and scatter into the tins.

Chop enough of remaining thyme leaves to make 1½ tablespoons, and combine with flour, salt and lemon zest in a bowl; whisk well.

Cream the butter until fluffy, add sugar and beat until pale. Add eggs, one at a time, mixing until smooth. Beat in lemon juice, then add flour mixture in three batches at low speed, mixing until just combined. Spoon into prepared cake pans, leveling the tops. Bake for 40 minutes, or until a skewer comes out clean. Set the pans on a rack, cool for 10 minutes, then unmould cakes.

To make lemon icing, combine icing sugar with lemon juice and stir until smooth. It should be drizzling consistency. If too thin, add more sugar; if too thick, add more lemon juice. Drizzle icing over cakes and scatter with extra thyme sprigs.