Preheat the oven to 100°C. Grease two baking sheets with nonstick spray, line with baking paper, grease and sift cornflour over.
1. Meringues Put the egg whites, sugar and tartaric acid in a glass bowl, then put the bowl on top of a saucepan with boiling water and simmer for 3 minutes or until warm and the sugar has dissolved. Remove from the heat and beat until light and shiny – about 10 minutes. Sift the cornflour over, add the rosewater, rosemary or lavender and fold into the egg mixture.
2. Spoon heaped tablespoonfuls (at least 20) of the egg-white mixture onto the prepared baking sheets and sprinkle the nuts over. Bake for 2 hours or until cooked on the outside. Switch the oven off and leave to cool in the oven overnight. Store in an airtight container.