Preheat the oven to 350°F, 175°C.
Line a large baking tray with nonstick baking paper and prepare 8 cups or ramekins on a work surface, near to where you will be taking the biscuits out of the oven, make sure the cups are up side down.
Whisk together the egg whites, sugar and pistachio nuts, until just combined, add in the melted butter and vanilla, continue whisking. Add the flour then cocoa to the mixture, whilst still whisking.
Using a tablespoon drop the mixture onto your paper and using the back of the spoon gently spread it into a thin layer, the mixture needs to be thin as the biscuits will not expand in the oven. Place in the pre-heated oven and cook for 12-13 minutes.
Using a spatula quickly remove the biscuits from the sheet and drape each one over a ramekin to form the shape, before placing on the upturned teacups to maintain the shape. If the biscuits start to go hard before you have finished shaping them, put them back in the oven to make them soft again.
Allow to cool completely before serving.
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