1. Preheat oven to 350°F (175°C).
2. In a small pot, combine the chocolate chips and oil. Cook on low, stirring until smooth.
3. In a standing mixer, beat the egg whites until stiff. In a separate bowl, whisk the yolks with the coconut sugar; add to melted chocolate and stir. Pour the chocolate mixture into the beaten egg whites and mix on medium speed until just combined.
4. Grease a round eight-inch (20-centimeter) springform pan with coconut oil. Pour in one-third of the mousse mixture and bake for 15 minutes.
5. Remove from the oven. (The mousse may rise while baking and then fall when cooling.) Top with remaining two-thirds of the mousse mixture. Cover and freeze until solid.
6. Remove from freezer 20 minutes before serving and slice.