Mississippi Mud Pie

Pastry

• 250 g plain flour, plus extra for dusting
• 125 g unsalted butter, cold, diced
• 30 g caster sugar
• 1 Tbsp cocoa powder
• 4 Tbsp water, ice cold

Filling

• 400 - 450 g natural frozen yoghurt
• 400 - 450 g chocolate frozen yoghurt
• 175 g caster sugar
• 3 egg whites, from large eggs