Preheat oven to 200 C and prepare muffin pan by greasing or fill with paper liners. A nonstick pan requires no greasing, although I like to just grease the bottoms. In large bowl mix well the eggs, oil, milk and vanilla. In smaller bowl mix well the flour, sugar, cocoa, baking powder, salt and chocolate chips. Combine wet and dry mixtures and fold together gently until just mixed. Spoon into prepared pan and sprinkle choc chips of top of each. Bake at 200C for 20 min. Remove from pan and cool on rack.