Preheat oven to 400F.
Meanwhile, place the chocolate and butter in a saucepan over LOW HEAT and stir until the chocolate is melted and smooth.
Generously butter four 125 ml (1/2 cup) capacity ramekins and set aside.
Whisk the eggs and sugar in a bowl until well combined and forms ribbons, about 6 minutes.
Add the chocolate mixture and hazelnut liquor. Whisk again at low speed.
Add the flour and fold until well combined.
Spoon the mixture into the ramekins until it fills just below the top line.
Place moulds/containers on a baking tray and bake for 10-12 minutes (depending on the power of your oven) OR until the cake springs back when you touch the surface with your finger. Unmould immediately onto serving plates and eat straight away in order to get the “lava effect”. You can also serve this lava cake with vanilla ice cream. Yum!