Line 2 baking sheets with nonstick baking paper and draw an 18 cm (7 inch) circle on each.
Whisk the egg whites in a large bowl until stiff, moist-looking peaks form. Mix the sugars together, then whisk in the sugar, a teaspoonful at a time, and continue whisking for 1–2 minutes until very thick and glossy (see
Divide the mixture between the lined baking sheets and spread into circles of even thickness between the marked lines. Bake in a preheated oven, 110°C (225°F), Gas Mark ¼, for 1½–1¾ hours or until the meringues may be easily lifted off the paper. Leave to cool in the switched-off oven.
Melt the chocolate (see
Whip the cream, when ready to serve, until it forms soft swirls, then fold in the yogurt and sugar. Put one of the meringue circles on a serving plate, chocolate-side up, spread with the cream, then arrange peach slices on top. Cover with the second meringue, chocolate-side down. Decorate the top with the remainder of the melted chocolate, drizzled randomly.