1. Make the raspberry purée first by pushing the raspberries through a nylon sieve into a small bowl, sift over the Tate & Lyle Icing Sugar and mix well until smooth. 
2. Preheat the oven to 200°C/Fan180°, 400°F, Gas Mark 6.
3. Tip the Tate & Lyle Golden Caster Sugar onto 1 of the baking trays and spread it out in an even layer. Warm through on the middle shelf of the oven for about 5-6 minutes or until the sugar feel hot to touch and has lightly coloured, stirring once. Don’t let it caramelize. Pour into a small bowl.
4. Reduce the oven heat down to its lowest, around 110°C/90°C Fan, 225°F, Gas Mark ¼.
5. As soon as the sugar is ready, using an electric mixer, add the whites to the bowl and whisk at high speed until they are light and foamy, for about 1 minute. Slowly add the hot sugar, a dessertspoon at a time, and continue whisking until the mixture has cooled and is very thick and glossy. Scrape down the sides halfway through. This will take about 10 minutes.
6. Use a little of the meringue to stick down the parchment paper on the remaining 2 baking trays. With 2 large spoons, divide the mixture into 10 large dollops, spacing them well apart on the trays as they almost double in size when baking. Drizzle each one with 1 teaspoon of the raspberry purée and then, using a fine skewer, swirl the purée through the surface of each meringue. If you fold it into the meringue mixture it will collapse.
7. Bake on the middle and top shelves of the oven for 1¾-2 hours, swapping the trays over halfway through. The meringues are ready when they are crisp on the outsides, the insides are still soft, and they sound hollow when the bottoms are tapped. Remove to a wire rack to cool, then store in an air-tight container.

You will also need 3 large baking trays lined with parchment paper.