1. In a large bowl, beat the softened butter, light brown sugar, and granulated sugar together until light and fluffy, about 2–3 minutes.

2. Add the egg and vanilla extract and mix until smooth, scraping down the sides of the bowl as needed.

3. In a separate bowl, whisk together the flour, cornstarch, baking soda, and fine sea salt until well combined.

4. Add the dry ingredients to the butter mixture in two additions, mixing on low speed just until the flour disappears and a soft dough forms.

5. Gently fold in the toffee bits until they are evenly distributed throughout the dough.

6. Cover the bowl and chill the dough in the refrigerator for at least 30 minutes and up to 24 hours for thicker, chewier cookies.

7. When ready to bake, preheat the oven to 350°F (175°C) and line baking sheets with parchment paper.

8. Scoop the chilled dough into 1 1/2-tablespoon balls and place them a couple of inches apart on the prepared baking sheets.

9. Bake for 9–11 minutes, or until the edges are lightly golden and the centers still look slightly soft.

10. Let the cookies cool on the baking sheet for 5 minutes, then transfer them to a wire rack to cool completely.

11. Place the chopped chocolate or wafers in a microwave-safe bowl and heat in 20–30 second bursts, stirring between each, until smooth and fully melted. Stir in the neutral oil if the chocolate seems very thick.

12. Dip each cooled cookie halfway into the melted chocolate, letting excess drip back into the bowl, then place on parchment paper.

13. While the chocolate is still wet, sprinkle the dipped side with extra toffee bits, chopped nuts, or a pinch of flaky sea salt.

14. Allow the chocolate to set completely at room temperature or in the refrigerator before serving or storing.