Preheat the oven to 190ºC/gas 5. Melt the butter, then lightly grease a 12-hole mini brioche or cupcake tin, dust with a little plain flour, then tap out the excess.
Sift the flour, baking powder and icing sugar into a bowl, then mix in the ground almonds.
In a separate bowl, whisk the egg whites with a pinch of sea salt until they form soft peaks. Add the sifted dry ingredients, as well as the oil and honey. Finely grate in the lemon zest, then fold it all together, until thoroughly combined.
Pour the batter into the tin holes, until they’re three-quarters full, and scatter over the flaked almonds.
Place the tins on a baking tray on the middle shelf of the oven and bake for 15 minutes, or until well risen and golden.
Leave them to cool in the tins for 2 minutes, before running a knife around the edges and turning them out onto a wire rack.
Meanwhile, prepare the syrup. Pare the zest off the lemons using a speed-peeler and slice it into fine strips. Squeeze the juice of both lemons into a bowl and set aside.
Blanch the lemon strips in boiling water for 1 minute, then drain and rinse under cold water. Return them to the pan with the lemon juice, sprigs of rosemary, sugar and 5 tablespoons of water. Gently bring it to the boil, then simmer, until reduced by half.
Remove the rosemary and slowly spoon the syrup (including the pared zest) over the warm cakes.
Pick a few rosemary leaves over each cake, leave to cool slightly, and serve.