For cake batter – in a bowl, whisk flour, corn starch, baking powder, baking soda and salt. In another bowl or mixer, beat soft butter and sugar until fluffy, about 2 minutes. Add vanilla. Add eggs one at a time until thoroughly combined. Add half of flour mixture and mix. Add half of coconut milk and mix. Add remaining flour and mix, then coconut milk and mix. Mix just until combined. Do not over mix.