Combine all-purpose flour, roughly cut chocolate chunks, sugar, cocoa, salt and baking powder in a mixing bowl. Create a well in the center.
Beat egg in a small bowl. Add milk, cooking oil, and vanilla. Stir and pour into well. Stir until just moistened.
Line a 12 cup muffin tin with liners. Fill cups ¾ full. Bake at 400°F for 20 minutes until a toothpick inserted comes out clean!