For the doughnuts, combine the yeast, water and a pinch of sugar in a small bowl and whisk to combine.
Place the milk in a saucepan over medium heat and bring to almost boiling, then remove from the heat. Place the butter, remaining sugar and a pinch of salt in a large bowl and pour in the hot milk. Whisk until all ingredients are dissolved, then set aside to cool.
When cool, add the yeast mixture, eggs and flour and mix until smooth. Cover and rest for 1 hour at room temperature.
While the batter rests, make the custard. Heat the milk, butter, 50g caster sugar, lemon zest and vanilla bean in a saucepan until almost boiling. Then pour over the chocolate buttons.
In a separate bowl, whisk the remaining sugar into the yolks then whisk in the cornflour and cocoa.
Add the chocolate and milk mix to the yolk mix and combine. Return to the saucepan and bring to just below the boil whisking constantly over a low heat.
Cook out for around 3 minutes, stirring constantly. Once the custard has thickened, add the almond essence and stir through. Serve straightaway or to store, pour into a bowl or container and press cling film onto the surface so a skin doesn’t form. To use the cold custard, whisk the set custard vigorously and then fold in whipped cream until the consistency comes back, serve.
To cook the doughnuts, heat the oil to 170°C in a deep fryer or large saucepan. Mix the cinnamon and caster sugar together. Using a spoon or ice cream scoop dipped in oil carefully drop the doughnut mixture into the hot oil. Turn after about 90 seconds and remove once evenly golden. Drop straight into the caster sugar and cinnamon mix and serve with the hot or cold custard.