Grease two ramekins with butter or coconut oil and preheat oven to 425 degrees.
Melt the chocolate chips and set aside.
Beat together the butter and sugar, then beat in the eggs.
Beat in tapioca flour and salt.
Slowly add the melted chocolate chips and stir in gently.
Pour evenly into two ramekins and bake for 10-11 minutes, until just the tops are set, and edges are slightly pulling away from sides. **Careful not to overcook, or you’ll lose the lava!**
Remove and let sit for about five minutes.
Turn over onto serving plate, and gently tap the bottom of the ramekin to get the cake to release.