Beat together butter and sugar until light and well combined
Add sifted flour and mix until it forms into crumbs
Add yolks and knead together to form into a dough (add water if needed to bring together)
Form into a ball, cover in plastic and chill for at least one hour
Roll out the pastry into a circle, approximately 5mm thick, and line a buttered 24cm flan tin
Return to the fridge to chill then blind bake the tart shell for 10/15 minutes or until golden brown
In a bowl, melt chocolate and butter together until combined then allow to cool slightly
In a mixer with the whisk attached, whisk the room temperature eggs, yolks and sugar on high until it becomes very thick and light in colour
Turn down mixer speed to low/medium and slowly and gradually add in the chocolate mixture
Mix for an additional 20-30 seconds, then very gently using a spatula, fold the mixture by hand until combined, being careful not to knock out too much of the air
Pour mixture into the pastry shell and bake for 15 minutes at 111°c fan forced oven
Allow to cool