1. In a bowl, put the eggs, sweetener and coffee.
2. Mix well.
3. Add the vanilla and yogurt.
4. Mix well again.
5. Add the flours, chocolate chips and baking powder.
6. Mix well again.
7. Transfer the mixture to (paper) muffin tins greased with olive oil.
8. Bake in a preheated oven at 180°C and bake for 12 minutes.
9. Prick with a fork; If it comes out dry, it's ready (if not, bake for 3 or 4 more minutes).
10. When it is cooked, remove and let cool to room temperature.