Cut rhubarb stalk into 2cm lengths and place into a saucepan with sugar and 1 cup water. Cook over low heat until rhubarb is soft but not broken down. Remove and strain; cool completely

Whisk egg yolks, milk, vanilla extract and melted butter together in a large jug

Combine custard powder, flour, baking powder and sugar together in a large mixing bowl and make a well in the centre

Carefully pour in egg and milk mixture and whisk until just combined. Fold through half the rhubarb and reserve the rest to serve

Beat egg whites with electric beaters until firm peaks form. Fold through waffle batter

Select BELGIAN waffle setting and dial up 5 on the browning control dial

Preheat until orange light flashes up and the word HEATING disappears

Using waffle dosing cup, pour 1/2 cup of batter into each waffle square. Close lid and cook until timer has finished and ready beep has sounded 3 times. Repeat with remaining batter

Serve warm with extra thick custard and reserved rhubarb and a sprinkle of icing sugar