Preheat oven to 350 degrees.Place muffin liners in tins, if using, or grease sides well.Whisk together the dry ingredients.Whisk together the wet ingredients.Mix wet into dry and stir until combined.Stir in mini chocolate chips, if using.Divide into muffin tins.Bake for around 15 minutes, or until toothpick comes out clean. (Bake longer if using regular-sized muffin tins.)