Start by mixing melted butter with brown sugar and granulated sugar until smooth. Add vanilla and eggs, mixing well after each addition. This step builds the base flavor and texture.
In a separate bowl, whisk flour, cornstarch, baking soda, and salt. Gradually mix the dry ingredients into the wet mixture until combined. Do not overmix, as this keeps the cookies tender.
Scoop the dough into equal portions and place them on a lined tray. Chill for at least 45 minutes. Chilling prevents spreading and improves flavor.
Preheat the oven to 350°F. Place chilled dough balls on a baking sheet with space between them. Bake for about 12 minutes until edges are set but centers remain soft.
Immediately after baking, gently reshape cookies if needed for a perfect round look. Let them cool on the baking sheet for a few minutes before transferring to a rack.
Melt the chocolate wafers in short intervals, stirring until smooth. Dip each cooled cookie halfway into the melted chocolate. Place on parchment paper and allow the chocolate to set completely.