1. Preheat the oven to 325°F (165°C) and line baking sheets with parchment paper.

2. In a large bowl, beat softened butter, powdered sugar, and granulated sugar until light and fluffy, about 2 to 3 minutes.

3. Stir in vanilla extract. In a separate bowl, whisk flour, cornstarch, and salt, then gradually add to the butter mixture and mix until a soft dough forms.

4. Fold in mini chocolate chips with a spatula until evenly distributed.

5. Shape the dough into a 2-inch diameter log or roll out to 1/2-inch thickness, wrap in plastic, and chill for at least 30 minutes.

6. Slice the chilled log into 1/4-inch rounds or cut shapes, place 1 inch apart on baking sheets, and bake for 14 minutes until edges are just golden.

7. Let cookies cool on the sheet for 5 minutes, then transfer to a cooling rack to cool completely.

8. Melt dipping chocolate in 30-second microwave bursts or over a double boiler until smooth and glossy.

9. Dip half of each cooled cookie into the melted chocolate, let excess drip off, then place on parchment and sprinkle toppings if desired. Allow to set.

10. Store cookies in an airtight container at room temperature for up to one week or freeze with layers separated by parchment paper.