• Preheat oven to 200°c - 390°f.
  
• Place the apples, rhubarb, unrefined caster sugar, ground cinnamon & the zest of 1 lemon into a large saucepan or pot. Place over medium heat mix to combine, cover & stew for 4 minutes. Remove the lid, mix to combine, cover & continue stewing for 3 minutes or until soft. Remove & let cool slightly.
  
• To make the crumble, add the plain (all-purpose) flour, unsalted butter, unrefined caster sugar & rolled oats (if using) to a mixing bowl. Mix together with clean hands rubbing the ingredients into the unsalted butter until it resembles coarse breadcrumbs.
  
• Pour the apple & rhubarb mix into a baking dish, top with the crumble mix & evenly spread it out. Run a fork across the top to create a rustic look (this will create a nice crispy top). Bake in the preheated oven for 28-30 minutes or until deeply golden, remove.
  
• Portion & serve in bowls. Pour over the creme anglasie (below) & dig in.
  

Creme Anglaise (Custard)

• In a mixing bowl, add in the egg yolks & unrefined caster sugar, whisk for 2-3 minutes or until pale & creamy.
  
• Add the milk, cream & vanilla to a medium-sized saucepan. Place over medium heat, whisk to combine & heat to 72°c - 161°f or just under simmering point (don't let it simmer or boil). Remove
  
• Pour the warmed mixture into the egg & sugar & vigorously whisk until combined. Pour the combined mixture back into the saucepan.
  
• Place the saucepan over low heat, whisk continuously for 5-6 minutes or until the creme anglaise (custard) coats the back of a spoon, remove & shock the bottom of the saucepan in a bowl filled with ice water (this will cool the creme anglaise and prevent it scrambling). Place in a bowl or bottle until ready to serve.