Preheat oven at 350F
Melt Chocolate and butter together using double boiling method on stove top at medium heat.
Sift flour and baking powder. Keep on side.
When chocolate and butter is melted, add condensed milk and vanilla extract.
Mix very well. Make sure there is no lumps and that mixture is smooth. For any reason, if any lumps left, run hand blender to break lumps. Turn off the stove and remove pot from the stove top.
Now, add flour mix and combine very well until smooth again.
Grease oven proof bowls with oil.
Pour batter into bowl.
Insert chocolate pieces inside to get lava.
Bake about 15-20 minutes or until done.