Rhubarb and custard with white chocolate mousse

Ingredients

Melt the chocolate over a bain marie. Whisk the egg white and sugar together until light and fluffy. When the chocolate has cooled slightly, fold in the egg white 7 and sugar mixture, being careful not to knock the air out. Slowly fold in the whipped cream. Place in fridge to set.
Chop up rhubarb to 2.5cm pieces and place in a pot of the cold sugar and water, ensuring there is enough poaching liquid to cover the rhubarb. You need equal amounts of sugar and water for the poaching liquid.
Place on a medium heat and slowly move the pot once in a while until it reaches just below boiling point, continue to keep an eye on it. Allow to cool in the liquid.
To make a rhubarb purée, take some of the poaching liquid and the rhubarb and blitz down until it reaches a purée consistency.
To make the custard, in a large pot bring the milk, cream and vanilla pod to a simmer. Whisk the yolks and the sugar until light in colour. Pour the hot milk cream onto the egg mixture, whisking constantly. Return to the pot over a low heat and stir until the mixture starts to thicken. Remove the pod before serving.
Reserve a handful of pistachios for serving, and blitz the remaining until a fine green powder is achieved.
To assemble, place a spoon of the white chocolate mousse in a bowl, surround the mousse with evenly placed pieces of rhubarb. Put a few spoons of pistachio crumb followed by the whole pistachios. Dot the custard and rhubarb purée around the bowl in a squeezy bottle. Serve.